Leetcode 62: Unique Paths - binomial coefficient optimised

leetcode_62e.cpp

#include <iostream>

using namespace std;

long long factorial(int n) {
    long long fact = 1;
    for (int i=2; i<=n; ++i)
        fact *= i;
    return fact;
}

int uniquePath(int m, int n) {
    int mx = max(m-1, n-1);
    int mn = min(m-1, n-1);
    long long dividend = 1;
    for (int i=1; i<=mn; ++i)
        dividend *= (mx+i);
    long long ret = dividend / factorial(mn);
    return (int)ret;
}

int main() {
    cout << uniquePath(23,12) << "\n";
    
    return 0;
}