leetcode 剑指 Offer 26. 树的子结构

0.code

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSubStructure(TreeNode A, TreeNode B) {
        if(B==null||A==null){
            return false;
        }
        return isSubStructureHelp1(A,B);
    }

    public boolean isSubStructureHelp1(TreeNode A, TreeNode B) {
        if(B==null||A==null){
            return false;
        }
        boolean flag = false;
        if(A.val==B.val){
            flag = isSubStructureHelp2(A.left,B.left)&&isSubStructureHelp2(A.right,B.right);
        }
        if(!flag){
            flag = isSubStructureHelp1(A.left,B)||isSubStructureHelp1(A.right,B); 
        }
        return flag;
    }

    public boolean isSubStructureHelp2(TreeNode A, TreeNode B) {
        if(A==null&&B==null){
            return true;
        }
        if(A==null&&B!=null){
            return false;
        }
        if(A!=null&&B==null){
            return true;
        }
        if(A.val!=B.val){
            return false;
        }
        if(isSubStructureHelp2(A.left,B.left)&&isSubStructureHelp2(A.right,B.right)){
            return true;
        }
        return false;
    }
}