HDU-Max Sum(dp)

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Max Sum

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

题目链接:

acm.hdu.edu.cn/showproblem…

题意描述:

这个题题意很简单,就是找一段连续的数字,要求它们的和最大,并输出该段数字的首尾下标。

解题思路:

我是先把它们存到数组中,存的过程中找到这n个数字的最大值如果最大值是小于等于0,那么就直接输出该数及其下标,否则就进行数字的累加,如果累加的和小于0了那么就把sum置为0,并暂时记录此刻的下标加1(加1的原因是该下标的值一定小于0,故暂且记录下一个下标暂为首下标),直到sum大于maxn更新maxn以及首尾下标。

程序代码:

这个代码我感觉有点麻烦,如果谁有简单一点的欢迎评论。

#include<stdio.h>
#include<string.h>
const int inf=99999999;
int a[100010];

int main()
{
	int T,i,n,m,f,f0,e,maxn,sum,count=1;
	scanf("%d",&T);
	while(T--)
	{
		maxn=-inf;
		scanf("%d",&n);
		for(i=1;i<=n;i++)	
		{
			scanf("%d",&a[i]);
			if(a[i]>maxn)
			{
				f=i;
				e=i;
				maxn=a[i];
			}
		}
		if(maxn<=0)
			printf("Case %d:\n%d %d %d\n",count++,maxn,f,e);
		else
		{
			f0=1;
			f=1;
			e=1;
			sum=0;
			maxn=0;
			for(i=1;i<=n;i++)
			{
				sum+=a[i];
				if(sum<0)
				{
					f0=i+1;
					sum=0;
				}
				if(sum>maxn)
				{
					maxn=sum;
					f=f0;
					e=i;
				}
			}
			printf("Case %d:\n%d %d %d\n",count++,maxn,f,e);	
		}
		if(T>0)
			printf("\n");
	}
	return 0;
}