hdu杭电1003 dp 连续子序列最大值
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.
题意:
输出连续子序列的最大值,且输出起点和终点
思路
我是参考了大佬的思路,自己纯暴力写超时,后来才知道是dp题。
先确定状态,用数组存储每一项的子序列最大值。状态转移方程,如果第i-1项大于0,则第i项的子序列最大值可以由第i-1项的值相加得到否则加0.
代码
#include<stdio.h>
#include<string.h>
#define N 100000
int num[N+10];
int main()
{
int t,i,n,x,sum,temp,end,start,max;
scanf("%d",&t);
x = t ;
while( t --)
{
scanf("%d",&n);
sum = 0;
temp = 1;
max = -1001;
memset(num,0,sizeof(num));
for( i = 1; i <= n; i ++)
{
scanf("%d",&num[i]);
sum += num[i];//printf("sum=%d\n",sum);
if( sum > max)
{
max = sum;
start = temp;
end = i;
}
if( sum < 0)
{
sum = 0;
temp = i + 1;
}
}
printf("Case %d:\n",x-t);
printf("%d %d %d\n",max,start,end);
if( x-t < x)
printf("\n");
}
return 0;
}
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