src2020/1666_erfen/main.cpp

#include <iostream>
using namespace std;
int a[100001];
void erfen(int tou, int wei, int n)
{
    int now = wei - tou;
    if (now < 0||tou>wei) {
        cout << "-1" << endl;
        return;
    }
    if (now == 0) {
        if (a[tou+now] == n) {
            cout << tou+now << endl;
            return;
        } else {
            cout << "-1" << endl;
            return;
        }
    }
    now /= 2;
    now+=tou;
    //cout<<tou<<" "<<wei<<" "<<now<<endl<<endl;
    if (a[now] == n) {
        cout << now << endl;
        return;
    }
    if (n>a[now]) {
        erfen(now + 1, wei, n);
        return;
    } else {
        //cout<<"<"; 
        erfen(1, now - 1, n);
        return ;
    }
}
int main()
{
    int zong, zhao;
    cin >> zong >> zhao;
    for (int i = 1; i <= zong; i++) {
        cin >> a[i];
    }
    for (int i = 1; i <= zhao; i++) {
        int now;
        cin >> now;
        erfen(1, zong, now);
       // cout<<now<<endl;
    }
}