Construct binary tree from inorder array and postorder array, assume items are unique

ConstructBinaryTreeFromInorderArrayAndPostorderArray.java

//2/4/2014 rewrite code

public class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        if (inorder==null||inorder.length==0||postorder==null ||postorder.length==0){
            return null;
        }
        
        int iSt=0;
        int iEd=inorder.length-1;
        
        int pSt=0;
        int pEd=postorder.length-1;
        
        return buildTree(inorder, iSt, iEd, postorder, pSt, pEd);
    }
    
    private TreeNode buildTree(int[] inorder, int iSt, int iEd, int[] postorder, int pSt, int pEd){
        if (iSt>iEd || pSt>pEd){
            return null;
        }
        
        TreeNode root=new TreeNode (postorder[pEd]);
        int index=0;
        
        for (int i=iSt; i<=iEd; i++){
            if (inorder[i]==root.val){
                index=i;
                break;
            }
        }
        
        int len=index-iSt;
        
        root.left=buildTree(inorder, iSt, index-1, postorder, pSt, pSt+len-1);
        root.right=buildTree(inorder, index+1, iEd, postorder, pSt+len-1+1, pEd-1);
        
        return root;
        
        
    }
}

/**
 * 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[] inorder, int[] postorder) {
        // Start typing your Java solution below
        // DO NOT write main() function
       int inorder_start=0;
       int inorder_end=inorder.length-1;
       
       int postorder_start=0;
       int postorder_end=postorder.length-1;
       
       return buildTree(inorder, inorder_start, inorder_end,
                        postorder, postorder_start, postorder_end
                        );
    }
    public TreeNode buildTree(int[] inorder, int inorder_start, int inorder_end,int[] postorder, int postorder_start, int postorder_end)
    {
        if (inorder_start>inorder_end||postorder_start>postorder_end){
            
            return null;            
        }
        int rootVal=postorder[postorder_end];
        TreeNode root= new TreeNode(rootVal);
        
        for (int i=inorder_start; i<=inorder_end; i++){
            
            if (inorder[i]==rootVal){
                
                TreeNode left=buildTree(inorder, inorder_start, i-1,
                                       postorder, postorder_start,
                                                  postorder_start+i-inorder_start-1);"Memoried the boundary case"
                TreeNode right=buildTree(inorder, i+1, inorder_end,
                                         postorder, postorder_end-inorder_end+i,postorder_end-1);"memoried the boundary case"
                root.left=left;
                root.right=right;
            }
        }
        
        return root;
                                  
                                  
                                  
                                  
    }
}