HDOJ1003.Max Sum

试题请参见: http://acm.hdu.edu.cn/showproblem.php?pid=1003

题目概述

Given a sequence a[1],a[2],a[3]……a[n], your job is to calculate the max sum of a sub-sequence. For example, given (6,-1,5,4,-7), the max sum in this sequence is 6 + (-1) + 5 + 4 = 14.

解题思路

最大子序列问题. 存在O(n)的解法.

遇到的问题

对于子序列(-100, -10, -1000)始终无法获得正确结果.

源代码

#include <iostream>const int MAX_SIZE = 100000;int arr[MAX_SIZE];int main() {    int t = 0;    std::cin >> t;    for ( int i = 1; i <= t; ++ i ) {        int n = 0;        std::cin >> n;        for ( int j = 0; j < n; ++ j ) {            std::cin >> arr[j];        }        int startIndex = 0, currentStartIndex = 0, endIndex = 0;        int maxSum = -2147483648, currentSum = 0;        for ( int j = 0; j < n; ++ j ) {            currentSum += arr[j];            if ( currentSum > maxSum ) {                startIndex = currentStartIndex;                endIndex = j;                maxSum = currentSum;            }            if ( currentSum < 0 ) {                currentStartIndex = j + 1;                currentSum = 0;            }        }        std::cout << "Case " << i << ":" << std::endl;        std::cout << maxSum << " " << startIndex + 1 << " " << endIndex + 1 << std::endl;        if ( i != t ) {            std::cout << std::endl;        }    }    return 0;}