The correct, optimal and working solution for programming question lowest-common-ancestor-of-a-binary-tree on leetcode

/* * Author: Arpit Bhayani * http://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; } struct node { int val; struct node * left; struct node *right; }; struct node * new_node(int val) { struct node *t = (struct node *) malloc(sizeof(struct node)); t->val = val; t->left = t->right = NULL; return t; } struct node * lowestCommonAncestor(struct node * root, struct node * p, struct node * q) { if(root == NULL) { return NULL; } if(root == p || root == q) { return root; } struct node * l = lowestCommonAncestor(root->left, p, q); struct node * r = lowestCommonAncestor(root->right, p, q); if(l && r) { return root; } if(l) return l; if(r) return r; return NULL; } int main(int argc, char *argv[]) { struct node * root = NULL; root = new_node(1); root->left = new_node(2); root->right = new_node(3); lowestCommonAncestor(root, root->left, root->left); return 0; }