注意左右边界的问题，若是右边界则mid需加一

C++ 代码

include<iostream>
using namesapce std;
const int N = 100010;
int n,m;
int q[N];
int main(){
    scanf("%d",&n,&m);
    for(int i = 0;i < 0;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) cout << "-1 -1" << endl;
        else {
        cout << l << ' ';
            int l = 0,r = n - 1;
            while(l < r){
                int mid = (l + r + 1) >> 1;
                if(q[mid] <= x) l = mid;
                else r = mid - 1;
            }
            cout << l << endl;
        }
    }
    return 0;
}