AC狗题解

#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    int x;
    cin >> x;

    int left = 0, right = n - 1;
    while (left <= right) {
        int mid = left + (right - left) / 2;
        if (a[mid] == x) {
            cout << mid + 1 << endl; // 下标从 1 开始
            return 0;
        } else if (a[mid] < x) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }

    cout << -1 << endl;
    return 0;
}