The correct, optimal and working solution for programming question binary-tree-level-order-traversal 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; } 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; } vector< vector<int> > levelOrder(struct node * root) { vector< vector<int> > v; if(root == NULL) { return v; } queue<struct node *> q; q.push(root); while(!q.empty()) { vector<int> level_vector; int s = q.size(); while(s--) { struct node * t = q.front(); q.pop(); level_vector.push_back(t->val); if(t->left) { q.push(t->left); } if(t->right) { q.push(t->right); } } v.push_back(level_vector); } return v; } int main(int argc, char *argv[]) { struct node * root = NULL; root = new_node(5); root->left = new_node(3); root->right = new_node(1); root->left->left = new_node(7); root->left->right = new_node(4); root->left->left->right = new_node(2); root->right->right = new_node(8); vector< vector<int> > v = levelOrder(root); return 0; }