1007. Maximum Subsequence Sum (25)

Given a sequence of K integers { N₁, N₂, ..., N_K }. A continuous subsequence is defined to be { N_i, N_i+1, ..., N_j } 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.

Sample Input:

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

Sample Output:

10 1 4

/*PAT 1007
求和最大的子序列
输入：k个数（k <= 10000)
输出要求：
当k个数全部都为负数时，和为0 ，输出序列的第一个和最后一个数字
两个子序列和相等时，输出下标较小的
可能出现WA的原因：注意检查下标记录是否正确
*/
#include <cstdio>
#define N 10001
using namespace std;
int index[N];
int dp[N];
int main(){
    int k;
    int sum = -1,minIndexL = 0,minIndexR = 0,tempIndex = 0,temp = 0;
    scanf("%d",&k);
    for(int i = 0;i < k;i++){   
        scanf("%d",&dp[i]);
        temp = temp + dp[i];
        if(temp < 0){
            temp = 0;
            tempIndex = i+1;
        }else{
            if(sum < temp){
                sum = temp;
                minIndexL = tempIndex;
                minIndexR = i;
            }
        }
    }
    //不需要在输入时检查是否为负，因为sum是最大和，最大值都小于0的话，必然全都为负
    if(sum >= 0){   
        printf("%d %d %d
",sum,dp[minIndexL],dp[minIndexR]);
    }else
        printf("0 %d %d
",dp[0],dp[k-1]);
}