折半查找题解

#include<bits/stdc++.h>
using namespace std;
int n,m,a[1000005],key,x;
int find(int key){
    int left=1,right=n,c;
    while(left<=right){
        c=(left+right)/2;
        if(a[c]<key) left=c+1;
        else if(a[c]>key) right=c-1;
        else{
            while(a[c-1]==key) c--;
            return c;
        }
    }
    return -1;
}
int main(){
    cin>>n>>m;
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int i=1;i<=m;i++){
        cin>>key;
        cout<<find(key)<<" ";
    }
    return 0;
}