1519. Number of Nodes in the Sub-Tree With the Same Label

https://leetcode.com/problems/number-of-nodes-in-the-sub-tree-with-the-same-label

You are given a tree (i.e. a connected, undirected graph that has no cycles) consisting of n nodes numbered from 0 to n - 1 and exactly n - 1 edges. The root of the tree is the node 0, and each node of the tree has a label which is a lower-case character given in the string labels (i.e. The node with the number i has the label labels[i]).

The edges array is given on the form edges[i] = [a_i, b_i], which means there is an edge between nodes a_i and b_i in the tree.

Return an array of size n where ans[i] is the number of nodes in the subtree of the ith node which have the same label as node i.

A subtree of a tree T is the tree consisting of a node in T and all of its descendant nodes.

Example 1

• Input: n = 7, edges = [[0,1],[0,2],[1,4],[1,5],[2,3],[2,6]], labels = "abaedcd"
• Output: [2,1,1,1,1,1,1]
• Explanation: Node 0 has label 'a' and its sub-tree has node 2 with label 'a' as well, thus the answer is 2. Notice that any node is part of its sub-tree. Node 1 has a label 'b'. The sub-tree of node 1 contains nodes 1,4 and 5, as nodes 4 and 5 have different labels than node 1, the answer is just 1 (the node itself).

Example 2

• Input: n = 4, edges = [[0,1],[1,2],[0,3]], labels = "bbbb"
• Output: [4,2,1,1]
• Explanation: The sub-tree of node 2 contains only node 2, so the answer is 1. The sub-tree of node 3 contains only node 3, so the answer is 1. The sub-tree of node 1 contains nodes 1 and 2, both have label 'b', thus the answer is 2. The sub-tree of node 0 contains nodes 0, 1, 2 and 3, all with label 'b', thus the answer is 4.

Example 3

• Input: n = 5, edges = [[0,1],[0,2],[1,3],[0,4]], labels = "aabab"
• Output: [3,2,1,1,1]

Constraints

• 1 <= n <= 10^5
• edges.length == n - 1
• edges[i].length == 2
• 0 <= a_i, b_i < n
• a_i != b_i
• labels.length == n
• labels is consisting of only of lowercase English letters.