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// 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<int> &parent, string s) {
int n = parent.size(), ans = 1;
queue<int> q;
vector<int> 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<int> 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
}
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