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preorder_inorder.java
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executable file
·31 lines (30 loc) · 1020 Bytes
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/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public TreeNode buildTree(int[] preorder, int[] inorder) {
// Start typing your Java solution below
// DO NOT write main() function
if(inorder.length==0 || preorder.length==0) return null;
int middle = preorder[0];
int index = -1;
for(int i=0;i<inorder.length;i++){
if(inorder[i]==middle){
index = i;
break;
}
}
TreeNode left = buildTree(Arrays.copyOfRange(preorder,1,index+1),Arrays.copyOfRange(inorder,0,index));
TreeNode right = buildTree(Arrays.copyOfRange(preorder,index+1,preorder.length),Arrays.copyOfRange(inorder,index+1,inorder.length));
TreeNode current = new TreeNode(middle);
current.left = left;
current.right = right;
return current;
}
}