Kindergarten

input/code.cpp: In function 'long long int backtracking(long long int (*)[17], long long int*, long long int, long long int, long long int, long long int, int)':
input/code.cpp:25:18: error: no matching function for call to 'std::unordered_map<std::pair<int, int>, long long int, PairHash>::find(std::string&)'
   25 |     if (memo.find(key) != memo.end()) return ans + memo[key];
      |         ~~~~~~~~~^~~~~
In file included from /usr/include/c++/11/unordered_map:47,
                 from /usr/include/c++/11/functional:61,
                 from /usr/include/c++/11/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/11/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:65,
                 from input/code.cpp:1:
/usr/include/c++/11/bits/unordered_map.h:868:7: note: candidate: 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::iterator std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::find(const key_type&) [with _Key = std::pair...

#include <bits/stdc++.h>
using namespace std;

const int MAXN = 17;
long long result = 1e18;
long long n;
long long a[MAXN][MAXN];
long long check[MAXN];

struct PairHash {
    template <typename T1, typename T2>
    size_t operator()(const pair<T1, T2>& p) const {
        auto hash1 = hash<T1>{}(p.first);
        auto hash2 = hash<T2>{}(p.second);
        return hash1 ^ (hash2 << 1);
    }
};

unordered_map<pair<int, int>, long long, PairHash> memo;

long long backtracking(long long a[MAXN][MAXN], long long check[MAXN], long long i, long long depth, long long ans, long long n, int mask) {
    if (depth == n) return ans;
    
    string key = to_string(mask) + "," + to_string(i);
    if (memo.find(key) != memo.end()) return ans + memo[key];
    
    long long best = 1e18;
    for (int j = 1; j <= n; j++) {
        if (!(mask & (1 << j))) { 
            best = min(best, backtracking(a, check, j, depth + 1, ans + a[i][j], n, mask | (1 << j)));
        }
    }
    
    memo[key] = best - ans; 
    return best;
}

void solve() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            cin >> a[i][j];
        }
    }
    for (int i = 1; i <= n; i++) check[i] = 0; 
    
    for(int i = 1; i <= n; i++) {
        int mask = (1 << i);
        result = min(result, backtracking(a, check, i, 1, a[i][i], n, mask));
    }
    
    cout << result;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    solve();
    
    return 0;
}