279C - Ladder - CodeForces Solution

#include <iostream>
#include <vector>

using namespace std;
void init() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
}

int main() {
    init();
    int n, test;
    cin >> n >> test;
    vector<int> data = { 0 };

    int temp;
    for (int i = 0; i < n; ++i) {
        cin >> temp;
        data.push_back(temp);
    }

    vector<int> Left(n + 1, 0);
    Left[1] = 1;
    vector<int> Right(n + 1, 0);
    Right[n] = n;

    for (int i = n - 1; i >= 1; --i) {
        if (data[i] <= data[i + 1]) {
            Right[i] = Right[i + 1];
        }
        else {
            Right[i] = i;
        }
    }


    for (int i = 2; i <= n; ++i) {
        if (data[i - 1] >= data[i]) {
            Left[i] = Left[i - 1];
        }
        else {
            Left[i] = i;
        }
    }

    int l, r;
    while(test--){
        cin >> l >> r;
        if (Left[r] <= Right[l]) {
            cout<<"Yes"<<endl;
        }
        else {
            cout<<"No"<<endl;
        }
    }

    return 0;
}