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LeetCode(106)Construct Binary Tree from Inorder and Postorder Traversal

程序员文章站 2022-05-20 13:53:02
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Given inorder and postorder traversal of a tree, construct the binary tree.

Note:
You may assume that duplicates do not exist in the tree.

public class Solution {
     public TreeNode build(int[]inorder,int instart,int inend,int[] postorder,int poststart,int postend){
        if(instart>inend||poststart>postend)
            return null;
        int val=postorder[postend];
        TreeNode root=new TreeNode(val);
        int index=0;
        for(int i=0;i<=inend;i++){
            if(inorder[i]==val){
                index=i;
            }
        }
        root.left=build(inorder,instart,index-1,postorder,poststart,poststart+index-instart-1);
        root.right=build(inorder,index+1,inend,postorder,poststart+index-instart,postend-1);
        return  root;

    }
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        if((inorder == null) ||(postorder == null) ||( inorder.length == 0 )|| (postorder.length == 0)) {
            return null;
        }
       return build(inorder,0,inorder.length-1,postorder,0,postorder.length-1);
    }
}