The correct, optimal and working solution for programming question unique-binary-search-trees on leetcode

/* * Author: Arpit Bhayani * https://arpitbhayani.me */ #include <cmath> #include <cstdio> #include <cstdlib> #include <climits> #include <deque> #include <iostream> #include <list> #include <limits> #include <map> #include <queue> #include <set> #include <stack> #include <vector> #define ll long long #define MIN(a, b) a < b ? a : b #define MAX(a, b) a > b ? a : b using namespace std; int readline(char *str) { int i = 0; char ch; while((ch = getchar()) != '\n') { str[i++] = ch; } str[i] = '\0'; return i; } int numTrees(int n) { int result = 0; int * count = (int *) calloc(n+1, sizeof(int)); count[0] = 1; count[1] = 1; for(int i = 2; i <= n; i++) { for(int j = 0; j < i; j++) { count[i] += count[j] * count[i - j - 1]; } } result = count[n]; free(count); return result; } int main(int argc, char *argv[]) { int n; scanf("%d", &n); printf("%d\n", numTrees(n)); return 0; }