diff --git a/LeetCode-CN/1.c b/LeetCode-CN/1.c
new file mode 100644
index 0000000..e99dc98
--- /dev/null
+++ b/LeetCode-CN/1.c
@@ -0,0 +1,46 @@
+#include <stdlib.h>
+#include <string.h>
+typedef struct pack
+{
+    int val;
+    int pos;
+}pack;
+
+int qcmp(const void* a, const void* b)
+{
+    return ((pack*)a)->val - ((pack*)b)->val;
+}
+
+int* twoSum(int* nums, int numsSize, int target) {
+    pack* p = (pack*)malloc(sizeof(pack)*numsSize);
+    for (int i = 0; i < numsSize; i++)
+    {
+        p[i].val = nums[i];
+        p[i].pos = i;
+    }
+    qsort(p, numsSize, sizeof(pack), qcmp);
+
+    int L = 0;
+    int R = numsSize - 1;
+    while (L < R)
+    {
+        int sum = p[L].val + p[R].val;
+        if (sum == target)
+        {
+            int* m = (int*)malloc(sizeof(int) * 2);
+            m[0] = p[L].pos;
+            m[1] = p[R].pos;
+            return m;
+        }
+        else if (sum < target)
+        {
+            L++;
+        }
+        else if (sum > target)
+        {
+            R--;
+        }
+    }
+    
+    return NULL;
+}
diff --git a/LeetCode-CN/1.cpp b/LeetCode-CN/1.cpp
new file mode 100644
index 0000000..a688b76
--- /dev/null
+++ b/LeetCode-CN/1.cpp
@@ -0,0 +1,41 @@
+#include <algorithm>
+
+bool cmp(const pair<int, int>& a, const pair<int, int>& b)
+{
+    return a.first < b.first;
+}
+
+class Solution {
+public:
+    vector<int> twoSum(vector<int>& nums, int target) {
+        int len = nums.size();
+        vector< pair<int, int> > vp;
+        for (int i = 0; i < len; i++)
+        {
+            vp.push_back(std::make_pair(nums[i], i));
+        }
+        sort(vp.begin(), vp.end(), cmp);
+        
+        int L = 0;
+        int R = len - 1;
+        while (L < R)
+        {
+            int sum = vp[L].first + vp[R].first;
+            if (sum == target)
+            {
+                vector<int> v;
+                v.push_back(vp[L].second);
+                v.push_back(vp[R].second);
+                return v;
+            }
+            else if (sum < target)
+            {
+                L++;
+            }
+            else if (sum > target)
+            {
+                R--;
+            }
+        }
+    }
+};
diff --git a/LeetCode-CN/146.cpp b/LeetCode-CN/146.cpp
new file mode 100644
index 0000000..3a94fdf
--- /dev/null
+++ b/LeetCode-CN/146.cpp
@@ -0,0 +1,89 @@
+#include <cstdlib>
+#include <cstring>
+#include <unordered_map>
+// DON'T USE STL LIST!! IT IS VERY SLOW!!!
+struct MyList
+{
+    int key, val;
+    MyList* pre;
+    MyList* next;
+};
+
+class LRUCache {
+public:
+    LRUCache(int capacity) {
+        maxsz = capacity;
+        sz = 0;
+        head = NULL;
+        end = NULL;
+    }
+
+    int get(int key) {
+        std::unordered_map<int, MyList*>::iterator iter = xp.find(key);
+        if (iter != xp.end())
+        {
+            MyList* tnode = iter->second;
+            if (tnode != head)
+            {
+                tnode->pre->next = tnode->next;
+                if (tnode->next)
+                {
+                    tnode->next->pre = tnode->pre;
+                }
+                else
+                {
+                    end = tnode->pre;
+                }
+                tnode->next = head;
+                tnode->pre = NULL;
+                head->pre = tnode;
+                head = tnode;
+            }
+            
+            return head->val;
+        }
+        else
+        {
+            return -1;
+        }
+    }
+
+    void put(int key, int value) {
+        if (get(key) != -1)
+        {
+            head->val = value;
+        }
+        else
+        {
+            MyList* xnode = (MyList*)malloc(sizeof(MyList));
+            xp.insert(std::make_pair(key, xnode));
+            xnode->key = key;
+            xnode->val = value;
+            xnode->pre = NULL;
+            xnode->next = head;
+            if(head) head->pre = xnode;
+            head = xnode;
+            if (end == NULL) end = head;
+
+            if (maxsz - sz)
+            {
+                sz++;
+            }
+            else
+            {
+                // keep sz 
+                xp.erase(end->key);
+                end = end->pre;
+                free(end->next);
+                end->next = NULL;
+            }
+        }
+    }
+private:
+    int maxsz;
+    int sz;
+    
+    std::unordered_map<int, MyList*> xp;
+    MyList* head;
+    MyList* end;
+};
diff --git a/LeetCode-CN/2.c b/LeetCode-CN/2.c
new file mode 100644
index 0000000..f5a00e4
--- /dev/null
+++ b/LeetCode-CN/2.c
@@ -0,0 +1,75 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     struct ListNode *next;
+ * };
+ */
+#ifdef __cplusplus
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#endif
+typedef struct ListNode ListNode;
+
+ListNode* BigIntegerAdd(ListNode* a, ListNode* b,
+    int* tmp)
+{
+    ListNode* pa = a;
+    ListNode* pb = b;
+    int pos = 0;
+    while (pa != NULL && pb != NULL)
+    {
+        tmp[pos] = pa->val + pb->val;
+        pa = pa->next;
+        pb = pb->next;
+        pos++;
+    }
+    while (pa != NULL)
+    {
+        tmp[pos] = pa->val;
+        pa = pa->next;
+        pos++;
+    }
+    while (pb != NULL)
+    {
+        tmp[pos] = pb->val;
+        pb = pb->next;
+        pos++;
+    }
+    ListNode* head = NULL;
+    ListNode** pthis = &head;
+    for (int i = 0; i < pos; i++)
+    {
+        if (tmp[i] >= 10)
+        {
+            tmp[i + 1] += tmp[i] / 10;
+            tmp[i] %= 10;
+        }
+
+        (*pthis) = (ListNode*)malloc(sizeof(ListNode));
+        (*pthis)->val = tmp[i];
+        (*pthis)->next = NULL;
+        pthis = &((*pthis)->next);
+    }
+
+    if (tmp[pos] > 0)
+    {
+        (*pthis) = (ListNode*)malloc(sizeof(ListNode));
+        (*pthis)->val = tmp[pos];
+        (*pthis)->next = NULL;
+        pthis = &((*pthis)->next);
+    }
+
+    return head;
+}
+
+struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
+    int tmp[1024];
+    memset(tmp, 0, sizeof(tmp));
+    return BigIntegerAdd(l1, l2, tmp);
+}
diff --git a/LeetCode-CN/2.cpp b/LeetCode-CN/2.cpp
new file mode 100644
index 0000000..feee5d8
--- /dev/null
+++ b/LeetCode-CN/2.cpp
@@ -0,0 +1,66 @@
+#ifdef __cplusplus
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#endif
+
+ListNode* BigIntegerAdd(ListNode* a, ListNode* b,
+    int* tmp)
+{
+    ListNode* pa = a;
+    ListNode* pb = b;
+    int pos = 0;
+    while (pa != NULL && pb != NULL)
+    {
+        tmp[pos] = pa->val + pb->val;
+        pa = pa->next;
+        pb = pb->next;
+        pos++;
+    }
+    while (pa != NULL)
+    {
+        tmp[pos] = pa->val;
+        pa = pa->next;
+        pos++;
+    }
+    while (pb != NULL)
+    {
+        tmp[pos] = pb->val;
+        pb = pb->next;
+        pos++;
+    }
+    ListNode* head = NULL;
+    ListNode** pthis = &head;
+    for (int i = 0; i < pos; i++)
+    {
+        if (tmp[i] >= 10)
+        {
+            tmp[i + 1] += tmp[i] / 10;
+            tmp[i] %= 10;
+        }
+
+        (*pthis) = new ListNode(tmp[i]);
+        pthis = &((*pthis)->next);
+    }
+
+    if (tmp[pos] > 0)
+    {
+        (*pthis) = new ListNode(tmp[pos]);
+        pthis = &((*pthis)->next);
+    }
+
+    return head;
+}
+
+
+class Solution {
+public:
+    ListNode * addTwoNumbers(ListNode* l1, ListNode* l2) {
+        int tmp[1024] = { 0 };
+        return BigIntegerAdd(l1, l2, tmp);
+    }
+};
diff --git a/LeetCode-CN/225.cpp b/LeetCode-CN/225.cpp
new file mode 100644
index 0000000..5eea112
--- /dev/null
+++ b/LeetCode-CN/225.cpp
@@ -0,0 +1,32 @@
+#include <list>
+class MyStack {
+public:
+    /** Initialize your data structure here. */
+    MyStack() {
+        
+    }
+
+    /** Push element x onto stack. */
+    void push(int x) {
+        lst.push_back(x);
+    }
+
+    /** Removes the element on top of the stack and returns that element. */
+    int pop() {
+        int t = lst.back();
+        lst.pop_back();
+        return t;
+    }
+
+    /** Get the top element. */
+    int top() {
+        return lst.back();
+    }
+
+    /** Returns whether the stack is empty. */
+    bool empty() {
+        return lst.empty();
+    }
+private:
+    std::list<int> lst;
+};
diff --git a/LeetCode-CN/25.cpp b/LeetCode-CN/25.cpp
new file mode 100644
index 0000000..d19dfb0
--- /dev/null
+++ b/LeetCode-CN/25.cpp
@@ -0,0 +1,70 @@
+#include <stack>
+class Solution {
+public:
+    ListNode * reverseKGroup(ListNode* head, int k) {
+        ListNode* seg_start = head;
+        ListNode* now = head;
+        ListNode* return_head = head;
+        ListNode* last_seg = NULL;
+        int passed = 0;
+
+        while (now != NULL)
+        {
+            passed++;
+            if (passed == k)
+            {
+                // Meet a segment
+                ListNode* seg_end = now;
+                // Change head
+                if (seg_start == head)
+                {
+                    return_head = seg_end;
+                }
+
+                ListNode* p = seg_start;
+                std::stack<ListNode*> stk;
+                while (p != seg_end)
+                {
+                    stk.push(p);
+                    p = p->next;
+                }
+                // p is now seg_end
+
+                // checkpoint
+                ListNode* next_seg_start = seg_end->next;
+
+                while (!stk.empty())
+                {
+                    p->next = stk.top();
+                    stk.pop();
+                    p = p->next;
+                }
+
+                // stack is empty. p is now seg_start. 
+                // p->next now pointes to the orignal "next"
+                
+                // set last segment
+                if (last_seg)
+                {
+                    last_seg->next = seg_end;
+                }
+                last_seg = seg_start;
+                // set it to next_seg_start
+                p->next = next_seg_start;
+
+                seg_start = next_seg_start;
+                now = next_seg_start;
+                passed = 0;
+
+                // debug
+                //printList(return_head);
+            }
+            else
+            {
+                now = now->next;
+            }
+        }
+
+        return return_head;
+    }
+};
diff --git a/LeetCode-CN/3.cpp b/LeetCode-CN/3.cpp
new file mode 100644
index 0000000..f34d73b
--- /dev/null
+++ b/LeetCode-CN/3.cpp
@@ -0,0 +1,38 @@
+#include <cstdlib>
+#include <cstring>
+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        int sz = s.size();
+        int bin[256];
+        int maxlen = 0;
+        int clen = 0;
+        int L = 0;
+        while (L < sz)
+        {
+            memset(bin, 0, sizeof(int) * 256);
+            int i;
+            for (i = L; i < sz; i++)
+            {
+                if (bin[s[i]])
+                {
+                    maxlen = clen > maxlen ? clen : maxlen;
+                    clen = 0;
+                    L++;
+                    break;
+                }
+                else
+                {
+                    bin[s[i]] = 1;
+                    clen++;
+                }
+            }
+            if (i == sz)
+            {
+                maxlen = clen > maxlen ? clen : maxlen;
+                break;
+            }
+        }
+        return maxlen;
+    }
+};
diff --git a/LeetCode-CN/32.cpp b/LeetCode-CN/32.cpp
new file mode 100644
index 0000000..2ffccae
--- /dev/null
+++ b/LeetCode-CN/32.cpp
@@ -0,0 +1,43 @@
+#include <algorithm>
+#include <stack>
+class Solution {
+public:
+    int longestValidParentheses(string s) {
+        int len = s.size();
+        int maxp = 0;
+        stack<int> stk;
+
+        for (int i = 0; i < len; i++)
+        {
+            if (s[i] == '(')
+            {
+                stk.push(i);
+            }
+            else // if (s[i] == ')')
+            {
+                // Stack not empty, and symbol matches.
+                if (!stk.empty() && s[stk.top()]=='(')
+                {
+                    // Pop matched pairs.
+                    stk.pop();
+                    if (stk.empty())
+                    {
+                        // From Start to i is a valid string.
+                        maxp = std::max(i + 1, maxp);
+                    }
+                    else
+                    {
+                        // From stk.top()+1 to i is a valid string. Length: i-(stk.top()+1)+1
+                        maxp = std::max(i - stk.top(), maxp);
+                    }
+                }
+                else
+                {
+                    // new start point (stub)
+                    stk.push(i);
+                }
+            }
+        }
+        return maxp;
+    }
+};
diff --git a/LeetCode-CN/3_beihe.cpp b/LeetCode-CN/3_beihe.cpp
new file mode 100644
index 0000000..271fb9f
--- /dev/null
+++ b/LeetCode-CN/3_beihe.cpp
@@ -0,0 +1,24 @@
+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        map<char, short> v;
+        int max_num = 0;
+        for (int i = 0; i < s.size(); ++i) {
+            if (v.find(s[i]) != v.end()) {
+                if (max_num < v.size()) {
+                    max_num = v.size();
+                }
+                i = v.find(s[i])->second + 1;
+                v.clear();
+            }
+            if (i >= s.size()) {
+                break;
+            }
+            v[s[i]] = i;
+            if (max_num < v.size()) {
+                max_num = v.size();
+            }
+        }
+        return max_num;
+    }
+};
diff --git a/LeetCode-CN/3_jzf.cpp b/LeetCode-CN/3_jzf.cpp
new file mode 100644
index 0000000..7fb8a1f
--- /dev/null
+++ b/LeetCode-CN/3_jzf.cpp
@@ -0,0 +1,39 @@
+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        int num =1;
+        int max =0;
+        if(s.length()==1)
+        {
+            return 1;
+        }
+        for(size_t i =0;i<s.length();i++)
+        {
+            
+            for(size_t j=i+1;j<s.length();j++)
+            {
+                int flag =0;
+                for(size_t k =i;k<j;k++)
+                {
+                    if(s[j]==s[k])   
+                    {
+                        flag =1;
+                        break;
+                    }
+                    num++;
+                }
+                    if(num>max)
+                    {
+                        max =num;
+                    }
+                if(flag ==1)
+                {
+                    break;
+                }
+                num =1;
+            }
+             num =1;
+        }
+        return max;
+    }
+};
diff --git a/LeetCode-CN/3_puck.cpp b/LeetCode-CN/3_puck.cpp
new file mode 100644
index 0000000..da22e8e
--- /dev/null
+++ b/LeetCode-CN/3_puck.cpp
@@ -0,0 +1,35 @@
+#include <algorithm>
+#include <string>
+#include <set>
+using std::string;
+class Solution
+{
+  public:
+    int lengthOfLongestSubstring(string s)
+    {
+        int result{};
+        for (std::size_t i{}; i < s.size(); ++i)
+        {
+            string tmp_str = s.substr(i);
+            int cu_length{};
+            std::set<char> set_except;
+            
+            for (auto ch : tmp_str)
+            {
+                if (set_except.end() == set_except.find(ch))
+                {
+                    set_except.insert(ch);
+                    ++cu_length;
+                }
+                else
+                {
+                    break;
+                }
+            }
+
+            result = std::max(result, cu_length);
+        }
+
+        return result;
+    }
+};
diff --git a/LeetCode-CN/4.cpp b/LeetCode-CN/4.cpp
new file mode 100644
index 0000000..73ccbb2
--- /dev/null
+++ b/LeetCode-CN/4.cpp
@@ -0,0 +1,77 @@
+#include <algorithm>
+class Solution {
+public:
+    void forward_until(vector<int>& nums1, vector<int>& nums2,
+        int lenA,int lenB,
+        int& idxA, int& idxB, int& passed, int midLen)
+    {
+        while (idxA < lenA&&idxB < lenB && passed < midLen)
+        {
+            if (nums1[idxA] < nums2[idxB])
+            {
+                idxA++;
+                passed++;
+            }
+            else
+            {
+                idxB++;
+                passed++;
+            }
+        }
+        while (idxA < lenA&&passed < midLen)
+        {
+            idxA++;
+            passed++;
+        }
+        while (idxB < lenB&&passed < midLen)
+        {
+            idxB++;
+            passed++;
+        }
+    }
+
+    int getCurrent(vector<int>& nums1, vector<int>& nums2, 
+        int lenA,int lenB,
+        int idxA, int idxB)
+    {
+        if (idxA < lenA&&idxB < lenB)
+        {
+            return std::min(nums1[idxA], nums2[idxB]);
+        }
+        else if (idxA < lenA)
+        {
+            return nums1[idxA];
+        }
+        else
+        {
+            return nums2[idxB];
+        }
+    }
+
+    double findMedianSortedArrays(vector<int>& nums1, vector<int>& nums2) {
+        int lenA = nums1.size();
+        int lenB = nums2.size();
+        int sumLen = lenA + lenB;
+        int midLen = sumLen / 2 - (1 - (sumLen % 2));
+        int idxA = 0;
+        int idxB = 0;
+        int passed = 0;
+        
+        forward_until(nums1, nums2, lenA, lenB, idxA, idxB, passed, midLen);
+
+        if (sumLen % 2)
+        {
+            return getCurrent(nums1, nums2, lenA, lenB, idxA, idxB);
+        }
+        else
+        {
+            int step1 = getCurrent(nums1, nums2, lenA, lenB, idxA, idxB);
+            
+            forward_until(nums1, nums2, lenA, lenB, idxA, idxB, passed, midLen + 1);
+            
+            int step2 = getCurrent(nums1, nums2, lenA, lenB, idxA, idxB);
+
+            return (step1 + step2) / 2.0;
+        }
+    }
+};
diff --git a/LeetCode-CN/494.cpp b/LeetCode-CN/494.cpp
new file mode 100644
index 0000000..177dab7
--- /dev/null
+++ b/LeetCode-CN/494.cpp
@@ -0,0 +1,36 @@
+class Solution {
+public:
+    int findTargetSumWays(vector<int>& nums, int S) {
+        if (S < -1000 || S>1000) return 0;
+
+        int sz = nums.size();
+        int msz = sizeof(int) * 2048;
+        int _bin[2048] = { 0 };
+        int _xbin[2048] = { 0 };
+        int* p = _bin;
+        int* q = _xbin;
+        memset(p, 0, msz);
+        p[1000] = 1;
+        
+        for (int i = 0; i < sz; i++)
+        {
+            memset(q, 0, msz);
+            for (int j = 0; j < 2048; j++)
+            {
+                if (p[j])
+                {
+                    //printf("p[%d]=%d\n", p[j]);
+                    // now=j-1000;
+                    int L = j - nums[i]; // now-nums[i]+1000
+                    int R = j + nums[i];
+                    q[L] += p[j];
+                    q[R] += p[j];
+                    //printf("q[%d]=%d\n", L, q[L]);
+                    //printf("q[%d]=%d\n", R, q[R]);
+                }
+            }
+            std::swap(p, q);
+        }
+        return p[S + 1000];
+    }
+};
diff --git a/LeetCode-CN/627.sql b/LeetCode-CN/627.sql
new file mode 100644
index 0000000..1d9cdce
--- /dev/null
+++ b/LeetCode-CN/627.sql
@@ -0,0 +1,4 @@
+    update salary set sex = case sex
+    when 'f' then 'm'
+    when 'm' then 'f'
+    end
diff --git a/LeetCode-CN/627_jzf.sql b/LeetCode-CN/627_jzf.sql
new file mode 100644
index 0000000..2d4f45e
--- /dev/null
+++ b/LeetCode-CN/627_jzf.sql
@@ -0,0 +1,2 @@
+update salary 
+    set sex = case when sex ='m' then 'f' else 'm' end;
diff --git a/LeetCode-CN/9.cpp b/LeetCode-CN/9.cpp
new file mode 100644
index 0000000..8a0ebdd
--- /dev/null
+++ b/LeetCode-CN/9.cpp
@@ -0,0 +1,37 @@
+#include <cstdio>
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        /*
+        // Converting to string is too slow!!
+        char buff[64] = { 0 };
+        sprintf(buff, "%d", x);
+        int len = strlen(buff);
+        int L = 0, R = len - 1;
+        while (L < R)
+        {
+            if (buff[L] != buff[R]) return false;
+            ++L;
+            --R;
+        }
+        return true;
+        */
+        if (x < 0) return false;
+        int buff[64] = { 0 };
+        int c = 0;
+        int tx = x;
+        while (tx > 0)
+        {
+            buff[c++] = tx % 10;
+            tx /= 10;
+        }
+        int L = 0, R = c - 1;
+        while (L < R)
+        {
+            if (buff[L] != buff[R]) return false;
+            ++L;
+            --R;
+        }
+        return true;
+    }
+};