Optimal sort

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <climits>
#include <unordered_map>

typedef long long ll;

using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    // freopen("input.txt", "r", stdin); // TODO: REMOVE THIS YOU STUPID ****

    int n;
    cin >> n;
    vector<int> orig(n);
    vector<int> nums(n);

    unordered_map<int, int> indices;

    for (int i = 0; i < n; i++) {
        cin >> nums[i];
        orig[i] = nums[i];
        indices[nums[i]] = i;
    }
    sort(nums.begin(), nums.end());

    int ans = 0;
    for (int i = 0; i < n; i++) {
        if (orig[i] == nums[i]) continue;
        ans += 1;
        int idx = indices[nums[i]];
        swap(orig[i], orig[idx]);
        indices[orig[idx]] = idx;
        indices[orig[i]] = i;
    }
    cout << ans;
}

Test 1

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