Subsequence

题目描述

A sequence of N positive integers (10 < N < 100 000), each of them less than or equal 10000, and a positive integer S (S < 100 000 000) are given. Write a program to find the minimal length of the subsequence of consecutive elements of the sequence, the sum of which is greater than or equal to S.

输入描述:

The first line is the number of test cases. For each test case the program has to read the numbers N and S, separated by an interval, from the first line. The numbers of the sequence are given in the second line of the test case, separated by intervals. The input will finish with the end of file.

输出描述:

For each the case the program has to print the result on separate line of the output file.if no answer, print 0.

输入

2
10 15
5 1 3 5 10 7 4 9 2 8
5 11
1 2 3 4 5

输出

2
3

题目大意

求一个最小长度的区间满足条件

思路

前缀和+尺举法(维护一个区间(差分))不断更新最小长度

#include <iostream> 
#include <algorithm>
#include <math.h>
using namespace std; 
int num[100000005];
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int n,sum;
        int minn=100000005;
        scanf("%d%d",&n,&sum);
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&num[i]);
            num[i]=num[i]+num[i-1];
        }
        int r=1;
        int l=1;
        while (r<=n)///边界条件
       {
           if (num[r]-num[l-1]>=sum)
           {
               minn=min((r-l+1),minn);///比较当前满足的子序列
               ++l;
           }
           else ++r;
       }
        if(minn==100000005)
        {
            printf("0\n");
        }else{
            printf("%d\n",minn);
        }
    }
    return 0;
 }