leetcode106

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        int len = postorder.length;
        if (len==0){
            return null;
        }
        int x = postorder[len-1];
        TreeNode root = new TreeNode(x);
        if (len==1){
            return root;
        }
        int index = -1;
        for(int i=0;i<len;i++){
           if (inorder[i]==x){
               index = i;
               break;
           } 
        }
        
        if (index>0){
            int[] leftInorder = new int[index];
            int[] leftPostorder = new int[index];
            for(int i=0;i<index;i++){
               leftInorder[i] =  inorder[i];
            }
            for(int i=0;i<index;i++){
               leftPostorder[i] =  postorder[i];
            }
            TreeNode left = buildTree(leftInorder,leftPostorder);
            root.left = left;   
        }
       
        if (len-1-index>0){
            int[] leftInorder = new int[len-1-index];
            int[] leftPostorder = new int[len-1-index];
            for(int i=0;i<len-1-index;i++){
               leftInorder[i] =  inorder[i+index+1];
            }
            for(int i=0;i<len-1-index;i++){
               leftPostorder[i] =  postorder[i+index];
            }
            TreeNode right = buildTree(leftInorder,leftPostorder);
            root.right = right; 
        }
        return root;     
    }
}