From 3b18366ca6cca93374ea2d9f612c8e87d2d36e5a Mon Sep 17 00:00:00 2001
From: Kirito <1362050620@qq.com>
Date: Tue, 13 Sep 2016 15:23:01 +0800
Subject: [PATCH] Create 3017.cpp

---
 POJ/3017.cpp | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 POJ/3017.cpp

diff --git a/POJ/3017.cpp b/POJ/3017.cpp
new file mode 100644
index 0000000..e5a76d9
--- /dev/null
+++ b/POJ/3017.cpp
@@ -0,0 +1,62 @@
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+#include <algorithm>
+using namespace std;
+
+#define MAXN 1000100
+#define INF 0x3f3f3f3f
+
+long long a[MAXN];
+long long dp[MAXN];
+
+long long t[MAXN];
+int tbegin,tend;
+
+int main()
+{
+    int N;
+    long long M;
+    scanf("%d %I64d",&N,&M);
+    tbegin=tend=0;
+    long long blocksum=0;
+    int blockbegin=0;
+    for(int i=1;i<=N;i++)
+    {
+        scanf("%I64d",&a[i]);
+        ///如果整个数列中任何一个数超过M，那么是无论如何都不能划分的(没有负数存在)
+        if(a[i]>M)
+        {
+            printf("-1\n");
+            return 0;
+        }
+        blocksum+=a[i];
+        while(blocksum>M)
+        {
+            ///如果现在假设的连续区块 ID: blockbegin, blockbegin+1 ... i
+            ///求和超过M，那么这是一个非法区块，需要减去最左端的区块(向右收缩)
+            blockbegin++;///【疑问】为什么blockbegin要在前面?
+            blocksum-=a[blockbegin];
+        }
+        ///队列用于维护每个区块中最大的值的ID
+        while(tbegin<tend&&a[t[tend-1]]<=a[i]) tend--;
+        t[tend++]=i;
+        ///队列中最左端的值的ID在blockbegin的左端，弹出
+        while(tbegin<tend&&t[tbegin]<=blockbegin) tbegin++;
+
+        ///未进行DP前初始化为INF
+        dp[i]=INF;
+
+        int maxvalbegin=blockbegin;
+
+        for(int index=tbegin;index<tend;index++)
+        {
+            long long tmp=dp[maxvalbegin]+a[t[index]];
+            dp[i]=min(dp[i],tmp);
+            maxvalbegin=t[index];
+        }
+    }
+    printf("%I64d\n",dp[N]);
+    return 0;
+}