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49 lines
3.1 KiB
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<p>You are given a tree (i.e. a connected, undirected graph that has no cycles) consisting of <code>n</code> nodes numbered from <code>0</code> to <code>n - 1</code> and exactly <code>n - 1</code> <code>edges</code>. The <strong>root</strong> of the tree is the node <code>0</code>, and each node of the tree has <strong>a label</strong> which is a lower-case character given in the string <code>labels</code> (i.e. The node with the number <code>i</code> has the label <code>labels[i]</code>).</p>
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<p>The <code>edges</code> array is given on the form <code>edges[i] = [a<sub>i</sub>, b<sub>i</sub>]</code>, which means there is an edge between nodes <code>a<sub>i</sub></code> and <code>b<sub>i</sub></code> in the tree.</p>
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<p>Return <em>an array of size <code>n</code></em> where <code>ans[i]</code> is the number of nodes in the subtree of the <code>i<sup>th</sup></code> node which have the same label as node <code>i</code>.</p>
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<p>A subtree of a tree <code>T</code> is the tree consisting of a node in <code>T</code> and all of its descendant nodes.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/07/01/q3e1.jpg" style="width: 400px; height: 291px;" />
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<pre>
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<strong>Input:</strong> n = 7, edges = [[0,1],[0,2],[1,4],[1,5],[2,3],[2,6]], labels = "abaedcd"
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<strong>Output:</strong> [2,1,1,1,1,1,1]
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<strong>Explanation:</strong> 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.
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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).
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/07/01/q3e2.jpg" style="width: 300px; height: 253px;" />
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<pre>
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<strong>Input:</strong> n = 4, edges = [[0,1],[1,2],[0,3]], labels = "bbbb"
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<strong>Output:</strong> [4,2,1,1]
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<strong>Explanation:</strong> The sub-tree of node 2 contains only node 2, so the answer is 1.
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The sub-tree of node 3 contains only node 3, so the answer is 1.
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The sub-tree of node 1 contains nodes 1 and 2, both have label 'b', thus the answer is 2.
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The sub-tree of node 0 contains nodes 0, 1, 2 and 3, all with label 'b', thus the answer is 4.
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/07/01/q3e3.jpg" style="width: 300px; height: 253px;" />
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<pre>
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<strong>Input:</strong> n = 5, edges = [[0,1],[0,2],[1,3],[0,4]], labels = "aabab"
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<strong>Output:</strong> [3,2,1,1,1]
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= n <= 10<sup>5</sup></code></li>
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<li><code>edges.length == n - 1</code></li>
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<li><code>edges[i].length == 2</code></li>
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<li><code>0 <= a<sub>i</sub>, b<sub>i</sub> < n</code></li>
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<li><code>a<sub>i</sub> != b<sub>i</sub></code></li>
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<li><code>labels.length == n</code></li>
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<li><code>labels</code> is consisting of only of lowercase English letters.</li>
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</ul>
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