The correct, optimal and working solution for programming question merge-point-ll on hackerrank

/* * 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 * new_node(int v) { struct Node * p = (struct Node *) calloc(1, sizeof(struct Node)); p->data = v; return p; } int FindMergeNode(Node * headA, Node * headB) { int lp = 0, lq = 0; struct Node * p = headA; struct Node * q = headB; while(p) { lp++; p = p->next; } while(q) { lq++; q = q->next; } p = headA; q = headB; if(lp > lq) { struct Node * t = p; p = q; q = t; int tt = lp; lp = lq; lq = tt; } for(int i = 0 ; i < (lq-lp); i++) { q = q->next; } while(p && q) { if(p == q) { return p->data; } p = p->next; q = q->next; } return 0; } int main(int argc, char *argv[]) { struct Node * head = new_node(1); head->next = new_node(2); head->next->next = new_node(3); cout << FindMergeNode(head) << endl; return 0; }