ACM1003:Max Sum
Problem Description
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.
Input
The first line of the input contains an integer T(1<=T<=20) which means the number of test cases. Then T lines follow, each line starts with a number N(1<=N<=100000), then N integers followed(all the integers
are between -1000 and 1000).
Output
For each test case, you should output two lines. The first line is "Case #:", # means the number of the test case. The second line contains three integers, the Max Sum in the sequence, the start position of the
sub-sequence, the end position of the sub-sequence. If there are more than one result, output the first one. Output a blank line between two cases.
Sample Input
2
5 6 -1 5 4 -7
7 0 6 -1 1 -6 7 -5
Sample Output
Case 1: 14 1 4
Case 2: 7 1 6
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/*
设a[i]为和最大序列的起点,则如果a[i]是负的,那么它不可能代表最优序列的起点,因为任何包含a[i]作为起点的子序列都可以通过a[i+1]作起点而得到改进。
类似的,任何负的子序列也不可能是最优子序列的前缀。
注意:如果全为负值,则取序列最大值。
*/
设a[i]为和最大序列的起点,则如果a[i]是负的,那么它不可能代表最优序列的起点,因为任何包含a[i]作为起点的子序列都可以通过a[i+1]作起点而得到改进。
类似的,任何负的子序列也不可能是最优子序列的前缀。
注意:如果全为负值,则取序列最大值。
*/
#include <stdio.h> #define SIZE 100100 int main() { //数据个数,数组长度。 int n, m; //序列 int a[SIZE]; int i, j, k; long long sum; long long max; int leftBorder, rightBorder, tempBorder; //freopen("F:\\input.txt","r",stdin); scanf("%d", &n); for (i = 0; i < n; i++) { sum = 0; max = -1001; memset(a, 0, sizeof(a)); leftBorder = rightBorder = tempBorder = 0; scanf("%d", &m); for (j = 0; j < m; j++) { scanf("%d", &a[j]); sum += a[j]; //如果当前和大于目前的最大和,则将sum设为最大和,并且更新边界 if (sum > max) { max = sum; leftBorder = tempBorder; rightBorder = j; } //如果当前和小于0,则当前序列不可能为最优序列的起点,重置和与边界 if (sum < 0) { sum = 0; tempBorder = j + 1; } } printf("Case %d:\n", i + 1); printf("%lld %d %d\n",max, leftBorder + 1, rightBorder + 1); if (i != (n - 1)) printf("\n"); } //freopen("con", "r", stdin); //system("pause"); return 0; }