The correct, optimal and working solution for programming question intersection-of-two-linked-lists 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 * next; }; struct node * new_node(int d) { struct node * t = (struct node *) calloc(1, sizeof(struct node)); t->val = d; return t; } void printList(struct node * head) { struct node * p = head; while(p) { printf("%d ", p->val); p = p->next; } printf("\n"); } struct node * getIntersectionNode(struct node * headA, struct node * headB) { struct node * a = headA; struct node * b = headB; int len_a = 0, len_b = 0; while(a) { len_a ++; a = a->next; } while(b) { len_b ++; b = b->next; } if(len_a < len_b) { struct node * temp = headA; headA = headB; headB = temp; int t = len_a; len_a = len_b; len_b = t; } a = headA; b = headB; for(int i = 0 ; i < (len_a - len_b); i++) { a = a->next; } struct node * result = NULL; while(a && b) { if(a == b) { result = a; break; } a = a->next; b = b->next; } return result; } int main(int argc, char *argv[]) { struct node * head = new_node(2); head->next = new_node(1); head->next->next = new_node(3); head->next->next->next = new_node(4); head->next->next->next->next = new_node(5); head->next->next->next->next->next = new_node(6); printList(head); head = getIntersectionNode(head, head); printList(head); return 0; }