Järjestäminen

input/code.cpp: In function 'void sort()':
input/code.cpp:18:9: warning: 'index' may be used uninitialized in this function [-Wmaybe-uninitialized]
     int index;
         ^~~~~

#include <iostream>
#include <vector>
 
using namespace std;

vector<int> v;

int n;

void swap(int a, int b) {
  int tmp = v[a];
  v[a] = v[b];
  v[b] = tmp;
}

void sort() {
  for (int i = 1; i <= n-4; i++) {
    int index;
    for (int j = 0; j < n; j++) {
      if (v[j] == i) {
        index = j;
        break;
      }
    }

    if (index < n-1) {
      // käännä niin että luku ensimmäinen parissa
      swap(i-1, index);
      swap(i, index+1);
    } else {
      // käännä niin että luku toinen parissa
      // index-3, index-2, index-1, index, index+1

      // 1 2 3 4
      // 3 4 1 2
      // uusi index = index - 2
      swap(index, index - 2);
      swap(index - 1, index - 3);

      swap(i-1, index-2);
      swap(i, index-1);
    }
    /*
    6 7 8


    */
  }

  if (v[n-1] != n) {
    swap(n-1, n-3);
    swap(n-2, n-4);
  }
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  
  int t; cin >> t;
  for (int ddd = 0; ddd < t; ddd++) {
    cin>>n;

    v.clear();
    v.resize(n);
    for (int i = 0; i < n; i++) cin >> v[i];

    if (n == 1) {
      cout << "YES";
    } else if (n == 2) {
      if (v[0] == 1) {
        cout << "YES";
      } else {
        cout << "NO";
      }
    } else if (n == 3) {
      if (v[0] == 1 && v[1] == 2) {
        cout << "YES";
      } else {
        cout << "NO";
      }
    } else if (n == 4) {
      if ((v[0] == 1 && v[1] == 2 && v[2] == 3 && v[3] == 4)
      || (v[0] == 3 && v[1] == 4 && v[2] == 1 && v[3] == 2)) {
        cout << "YES";
      } else {
        cout << "NO";
      }
    } else {
      sort();
      bool sorted = true;
      for (int i = 0; i < n; i++) {
        if (v[i] != i+1) sorted = false;
      }

      if (sorted) {
        cout << "YES";
      } else {
        cout << "NO";
      }
    }

    cout << "\n";
  }
}

Test 1

Group: 1, 2

Verdict: WRONG ANSWER

Test 2

Group: 2

Verdict: WRONG ANSWER

Test 3

Group: 1, 2

Verdict: WRONG ANSWER

Test 4

Group: 1, 2

Verdict: WRONG ANSWER