## Algoritmo de Determinant.

Cualquier duda no dudes en contactar.

``````/**
* Author: Simon Lindholm
* Date: 2016-09-06
* Source: folklore
* Description: Calculates determinant of a matrix. Destroys the matrix.
* Status: somewhat tested on https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&category=&problem=625 (ll and long double)
* Time: \$O(N^3)\$
*/
#pragma once

double det(vector<vector<double>>& a) {
int n = sz(a); double res = 1;
FOR(i,0,n) {
int b = i;
FOR(j,i+1,n) if (fabs(a[j][i]) > fabs(a[b][i])) b = j;
if (i != b) swap(a[i], a[b]), res *= -1;
res *= a[i][i];
if (res == 0) return 0;
FOR(j,i+1,n) {
double v = a[j][i] / a[i][i];
if (v != 0) FOR(k,i+1,n) a[j][k] -= v * a[i][k];
}
}
return res;
}

ll det(vector<vector<ll>>& a, ll mod) {
int n = sz(a); ll ans = 1;
FOR(i,0,n) {
FOR(j,i+1,n) {
while (a[j][i] != 0) { // gcd step
ll t = a[i][i] / a[j][i];
if (t) FOR(k,i,n)
a[i][k] = (a[i][k] - a[j][k] * t) % mod;
swap(a[i], a[j]);
ans *= -1;
}
}
ans = ans * a[i][i] % mod;
if (!ans) return 0;
}
return (ans + mod) % mod;
}
``````