57 lines
1.6 KiB
Java
57 lines
1.6 KiB
Java
package com.cool.hot100.binary_tree;
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import org.junit.Test;
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import java.util.HashMap;
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import java.util.Map;
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/**
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* Created with IntelliJ IDEA.
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*
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* @Author: Cool
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* @Date: 2024/09/01/19:34
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* DayNumber 2
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* Hard 2
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* Level 5
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*/
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public class Num105 {
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Map<Integer, Integer> map = new HashMap<>();
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public TreeNode buildTree(int[] preorder, int[] inorder) {
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for (int i = 0; i < inorder.length; i++) {
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map.put(inorder[i], i);
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}
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return buildTree(preorder, 0, 0, inorder.length - 1);
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}
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public TreeNode buildTree(int[] preorder, int indexInPre, int startInIn, int endInIn) {
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if (startInIn > endInIn) return null;
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TreeNode node = new TreeNode(preorder[indexInPre]);
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Integer headInIn = map.get(preorder[indexInPre]);
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int leftLength = headInIn - startInIn;
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node.left = buildTree(preorder,indexInPre+1,startInIn,headInIn-1);
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node.right=buildTree(preorder,indexInPre+leftLength+1,headInIn+1,endInIn);
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return node;
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}
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@Test
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public void test() {
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// TreeNode node1 = new TreeNode(6);
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// TreeNode node2 = new TreeNode(2);
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// TreeNode node3 = new TreeNode(4);
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// TreeNode node4 = new TreeNode(3);
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// TreeNode node5 = new TreeNode(5);
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// TreeNode node6 = new TreeNode(2);
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// TreeNode node7 = new TreeNode(1);
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// node7.left = node6;
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// node7.right = node5;
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// node6.left = node4;
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// node6.right = node3;
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// node5.right = node1;
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buildTree(new int[]{3, 9, 20, 15, 7}, new int[]{9, 3, 15, 20, 7});
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}
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}
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