2020 Winter Holiday [gmoj1592] [GDKOI Training] [Music Beat] [Prefix and + Two Points]

Title description

FJ is going to teach his cow to play a song. The song is composed of N (1 <= N <= 50,000) syllables, numbered 1 to N, and must be played in order from 1 to N, the i The syllable lasts B_i (1 <= B_i <= 10,000) beats, the beats are counted from 0, so the first syllable is played from beat 0 to beat B_1-1, from B_1 to B_1 + B_2-1 It is the second syllable, and so on.
Recently cows are not interested in playing the piano, they feel too boring. So in order to keep the cows focused, FJ asked Q (1 <= Q <= 50,000) questions, the format of the question is "what syllable is played in the Tth beat",
each question corresponds to a T_i (0 <= T_i <= Total number of beats-1) Please help the cow to solve it.

Input

In the first line, enter two space-separated integers N and Q.
Lines 2 to N + 1 each line contains an integer B_i line
N + 2-N + Q + 1 line each line contains an integer T_i

Output

The output has Q lines, and each line outputs the answer to the corresponding question.

Sample input

3 5
2
1
3
2
3
4
0
1

Sample output

2
3
3
1
1

analysis

Violence is easy to think about, but it times out.
Positive solution: Find the a [x] binary after the a array prefix and the binary search, and output mid or l.

Code on

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int n,q,a[100001];
int main()
{
	freopen("mnotes.in","r",stdin);
	freopen("mnotes.out","w",stdout);
    cin>>n>>q;
    for(int i=1;i<=n;i++)
    {
    	scanf("%d",&a[i]);
    	a[i]=a[i-1]+a[i];//前缀和
	}
	for(register int i=1;i<=q;i++)
	{
		int x; 
		scanf("%d",&x);
		x++;
		int l=1,r=n,ff=0,mid;
		while(l<=r)//二分找a[x]
		{
			mid=(l+r)/2;
			if(a[mid]>x)
			{
				r=mid-1;
			}
			if(a[mid]<x)
			{
				l=mid+1;
			}
			if(a[mid]==x)
			{
				printf("%d\n",mid);
				ff=1;
				break;
			}
		}
		if(!ff) printf("%d\n",l);
	}
	fclose(stdin);
	fclose(stdout);
    return 0;
}