Sorting

input/code.cpp: In function 'void dfs(std::vector<int>)':
input/code.cpp:70:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0 ; i + 1 < cur.size(); i ++ ){
                     ~~~~~~^~~~~~~~~~~~
input/code.cpp:71:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int j = i + 2; j + 1 < cur.size(); j ++ ){
                            ~~~~~~^~~~~~~~~~~~

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

#define fi first
#define se second
#define mp make_pair

map<vector<int>,int> can;

void solve(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(int i = 0 ; i < n; i ++ ){
        cin >> a[i];
        a[i]--;
    }
    if(n <= 3){
        if(a[0] < a[1] && a[1] < a[2]){
            cout << "YES\n";
        }
        else{
            cout << "NO\n";
        }
        return;
    }
    else if(n == 4){
        if(a[0] < a[1] && a[2] < a[3] && (a[1] < a[2] || a[3] < a[0])){
            cout << "YES\n";
        }
        else{
            cout << "NO\n";
        }
        return;
    }
    for(int i = 0 ; i < n-5; i ++ ){
        if(a[i] == i) continue;
        if(a[n - 1] == i){
            if(n - 1 - i >= 4){
                swap(a[n - 1], a[n - 3]);
                swap(a[n - 2], a[n - 4]);
            }
        }
        for(int j = i + 1; j < n; j ++ ){
            if(a[j] == i){
                swap(a[i],a[j]);
                swap(a[i+1],a[j+1]);
                break;
            }
        }
    }
    vector<int> d;
    for(int j = n - 5; j < n; j ++ ){
        d.push_back(a[j]-(n-5));
    }
    if(can.count(d)){
        cout << "YES\n";
    }
    else{
        cout << "NO\n";
    }
}

void dfs(vector<int> cur){
    can[cur]=1;
    for(int i = 0 ; i + 1 < cur.size(); i ++ ){
        for(int j = i + 2; j + 1 < cur.size(); j ++ ){
            swap(cur[i], cur[j]);
            swap(cur[i + 1], cur[j + 1]);
            if(!can.count(cur)){
                dfs(cur);
            }
            swap(cur[i], cur[j]);
            swap(cur[i + 1], cur[j + 1]);
        }
    }
}

int main(){
    vector<int> q(5);
    for(int i = 0 ;i < 5; i ++ ){
        q[i]=4-i;
    }
    dfs(q);
    int tc;
    cin >> tc;
    for(int t = 1; t <= tc; t ++ ){
        solve();
    }
}

Test 1

Group: 1, 2

Verdict: WRONG ANSWER

Test 2

Group: 2

Verdict: WRONG ANSWER

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED