main.cpp

#include <iostream>
#include <vector>


using namespace std;


int maximumGap(const vector<int> &num) {
    if (num.size() == 0) return -1;
    if (num.size() == 1) return 0;
    vector<pair<int, int> > toSort;
    for (int i = 0; i < num.size(); i++) {
        toSort.push_back(make_pair(num[i], i));
    }
    sort(toSort.begin(), toSort.end());
    int len = toSort.size();
    int maxIndex = toSort[len - 1].second;
    int ans = 0;
    for (int i = len - 2; i >= 0; i--) {
        ans = max(ans, maxIndex - toSort[i].second);
        maxIndex = max(maxIndex, toSort[i].second);
    }
    return ans;
}

int main() {

    vector<int> A = {3, 5, 4, 2};

    cout << maximumGap(A);
    

}