1007 Maximum Subsequence Sum (25分)

2020-07-27

1. 题目

Given a sequence of K integers { N1 , N2 , …, NK }. A continuous subsequence is defined to be { Ni , Ni+1 , …, Nj } where 1≤i≤j≤K. The Maximum Subsequence is the continuous subsequence which has the largest sum of its elements. For example, given sequence { -2, 11, -4, 13, -5, -2 }, its maximum subsequence is { 11, -4, 13 } with the largest sum being 20.

Now you are supposed to find the largest sum, together with the first and the last numbers of the maximum subsequence.

Input Specification:
Each input file contains one test case. Each case occupies two lines. The first line contains a positive integer K (≤10000). The second line contains K numbers, separated by a space.

Output Specification:
For each test case, output in one line the largest sum, together with the first and the last numbers of the maximum subsequence. The numbers must be separated by one space, but there must be no extra space at the end of a line. In case that the maximum subsequence is not unique, output the one with the smallest indices i and j (as shown by the sample case). If all the K numbers are negative, then its maximum sum is defined to be 0, and you are supposed to output the first and the last numbers of the whole sequence.

2. 样例输入

10 -10 1 2 3 4 -5 -23 3 7 -21

3. 样例输出

10 1 4

4. 思路

这一题是在慕课上讲过的
所以思路非常简单,寻找最长连续子列和就从做往右一直加,如果小于零了就舍弃进一步,然后就可以辣
还有就是注意审题,题目说如果找不到就输出第一和最后一个数字,之前的代码就是卡在这里

5. AC代码

#include <iostream>
#include <vector>
using namespace std;

int main() {
	int n; cin >> n;
    vector<int>v(n);
	int Thissum = 0, result = -1, head = 0, tail = n-1, temphead=0, temp=0;
	for (int i = 0; i < n; i++) {
		scanf("%d",&v[i]);
        temp+=v[i];
        if(temp<0){
            temp=0;
            temphead=i+1;
        }else if(temp>result){
            result=temp;
            head=temphead;
            tail=i;
        }
	}
	if(result<0)result=0;
	printf("%d %d %d",result,v[head],v[tail]);
    system("pause");
	return 0;
}