1007_Maximum Subsequence Sum (25分)[动态规划/最大和子序列]

题意: 输出子序列的最大和以及子序列的首尾元素.如果存在多个最大和子序列取位置最靠左的那个.如果序列元素全<0,和为0,输出给定序列的首尾元素.

 1 #include<iostream>
 2 #include<vector>
 3 #include<queue>
 4 #include<map>
 5 #include<set>
 6 #include<cmath>
 7 #include<cstdio>
 8 #include<cstdlib>
 9 #include<cstring>
10 #include<algorithm>
11 using namespace std;
12 
13 const int maxLen = 10000 + 10;
14 int val[maxLen], dp[maxLen], front[maxLen], N, maxSum, maxR;
15 
16 int main()
17 {
18     cin >> N;
19     memset(dp, 0, sizeof(dp));
20     memset(val, 0, sizeof(val));
21     memset(front, 0, sizeof(front));
22     for (int i = 0; i < N; i++) {
23         cin >> val[i];
24         dp[i] = val[i];
25         front[i] = i;
26     }
27     maxSum = dp[0]; maxR = 0; //初始化
28     for (int i = 1; i < N; i++) {
29         if (dp[i - 1] >= 0) { //动态规划
30             dp[i] = dp[i] + dp[i - 1];
31             front[i] = front[i - 1];
32         }
33         if (dp[i] > maxSum) { //记录:最靠左的最大子序列
34             maxSum = dp[i];
35             maxR = i;
36         }
37     }
38     if (maxSum < 0) {
39         cout << 0 << " " << val[0] << " " << val[N - 1] << endl;
40     }
41     else {
42         cout << maxSum << " " << val[front[maxR]] << " " << val[maxR] << endl;
43     }
44     return 0;
45 }