Add leetcode 673

LeetCode-CN/673.cpp

@@ -0,0 +1,43 @@
+
+class Solution {
+public:
+    int findNumberOfLIS(vector<int>& nums) {
+        int N = nums.size();
+        vector<pair<int, int>> dp(N);  // 以i为结尾的LIS长度, 这个长度出现的次数
+        for (int i = 0; i < N; i++) {
+            dp[i] = { 1,1 };
+        }
+        for (int i = 1; i < N; i++) {
+            int count = 1;
+            int maxLastLen = 0;
+            for (int j = 0; j < i; j++) {
+                if (nums[i] > nums[j]) {
+                    if (dp[j].first == maxLastLen)
+                    {
+                        count += dp[j].second;
+                    }
+                    else if (dp[j].first > maxLastLen) {
+                        count = dp[j].second;
+                        maxLastLen = dp[j].first;
+                    }
+                }
+            }
+            dp[i].first = maxLastLen + 1;
+            dp[i].second = count;
+        }
+
+        int maxFirst = 0;
+        for (auto& p : dp) {
+            maxFirst = max(maxFirst, p.first);
+        }
+
+        int cntSecond = 0;
+        for (auto& p : dp) {
+            if (p.first == maxFirst) {
+                cntSecond += p.second;
+            }
+        }
+
+        return cntSecond;
+    }
+};