为什么全是wa，求助

Kayleeeee @ 2024-02-29 23:30:05

#include<stdio.h>

const int N = 1e6 + 5;
int n, m;
int q[N];

int main()
{
    scanf("%d %d", &n, &m);
    for (int i = 1; i <= n; i++) scanf("%d", &q[i]);
    while (m--)
    {
        int x;
        scanf("%d", &x);

        int l = 0, r = n - 1;
        while (l < r)
        {
            int mid = l + r>>1;
            if (q[mid] >= x) r = mid; 
            else l = mid + 1;
        }
        if (q[l] != x) printf("-1");
        else printf("%d ", l);
    }
    return 0;
}

by syp11 @ 2024-03-01 00:20:22

两个问题

一个是输出-1后要加空格

另个是数据的标号是从1到n，所以二分的时候左右端点也应该是1到n

hack数据

3 5
1 2 3
0 1 2 3 4 5

改好的

#include<stdio.h>

const int N = 1e6 + 5;
int n, m;
int q[N];

int main()
{
    scanf("%d %d", &n, &m);
    for (int i = 1; i <= n; i++) scanf("%d", &q[i]);
    while (m--)
    {
        int x;
        scanf("%d", &x);

        int l = 1, r = n ;
        while (l < r)
        {
            int mid = l + r>>1;
            if (q[mid] >= x) r = mid; 
            else l = mid + 1;
        }
        if (q[l] != x) printf("-1 ");
        else printf("%d ", l);
    }
    return 0;
}

@Kayleeeee

by Kayleeeee @ 2024-03-01 13:29:12

@shiyupeng 好的，谢谢