// 2246. Longest Path With Different Adjacent Characters #include "leetcode.h" /* * you are given a tree (ie. a connected undirected graph that has no cycles) * rooted at node '0' consisting of 'n' nodes numbered from '0' to 'n - 1'. the * tree is represented by a 0-indexed array 'parent' of size 'n' where * 'parent[i]' is the parent of node 'i'. since node 0 is the root, 'parent[0] = * -1'. you are also given a string 's' of length 'n', where 's[i]' is the * character assigned to node 'i'. return the legnth of the longest path in the * tree such that no pair of adjacnet nodes on the path have the same character * assigned to them. */ class Solution { public: int longestPath(vector &parent, string s) { int n = parent.size(), ans = 1; queue q; vector cnt(n), top1(n, 1), top2(n, 1); for (int i = 1; i < n; ++i) ++cnt[parent[i]]; for (int i = 1; i < n; ++i) if (!cnt[i]) q.push(i); while (!q.empty() && q.front()) { int i = q.front(), p = parent[i]; q.pop(); if (int len = 1 + (s[i] != s[p] ? top1[i] : 0); top1[p] <= len) { top2[p] = top1[p]; top1[p] = len; } else top2[p] = max(top2[p], len); if (--cnt[p] == 0) { q.push(p); ans = max(ans, top1[p] + top2[p] - 1); } } return ans; } }; int main() { Solution obj; vector p1 = {-1, 0, 0, 1, 1, 2}, p2 = {-1, 0, 0, 0}; printf("%d\n", obj.longestPath(p1, "abacbe")); // expect: 3 printf("%d\n", obj.longestPath(p2, "aabc")); // expect: 3 }