题解 | #【模板】二分#

#include "bits/stdc++.h"
//注意原区间为左闭右开！（我就是因为这个wa了好几发，哭了）
using namespace std;
#define int long long
#define endl "\n"
#define PII pair<int,int>
#define PIII pair<int,PII>
const int MOD = 1e9 + 7;
const int N = 3e5;

void slu() {
    int n, m;
    cin >> n >> m;
    vector<int> a(n);
    for (int i = 0; i < n; i++)cin >> a[i];
    for (int i = 0; i < m; i++) {
        int t;
        cin >> t;
        if (t == 1) {
            int l, r, x;
            cin >> l >> r >> x;
            auto it = std::lower_bound(a.begin() + l, a.begin() + r, x);
            if (it < a.begin() + l || it >= a.begin() + r)cout << -1 << endl;
            else cout << *it << endl;
        } else if (t == 2) {
            int l, r, x;
            cin >> l >> r >> x;
            auto it = std::upper_bound(a.begin() + l, a.begin() + r, x);
            if (it < a.begin() + l || it >= a.begin() + r)cout << -1 << endl;
            else cout << *it << endl;
        } else if (t == 3) {
            int l, r, x;
            cin >> l >> r >> x;
            auto it = std::lower_bound(a.begin() + l, a.begin() + r, x);
            it--;
            if (it < a.begin() + l || it >= a.begin() + r)cout << -1 << endl;
            else cout << *it << endl;
        } else {
            int l, r, x;
            cin >> l >> r >> x;
            auto it = std::upper_bound(a.begin() + l, a.begin() + r, x);
            it--;
            if (it < a.begin() + l || it >= a.begin() + r)cout << -1 << endl;
            else cout << *it << endl;
        }
    }
}

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int T;
//    cin >> T;
    T = 1;
    while (T--)slu();

}