Given two binary trees, write a function to check if they are equal or not.
Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
解题：还是简单的递归，把情况考虑清楚就可以了：
根节点都为空，树相同；
根节点一方为空，另一方不为空，树不相同；
根节点值不想等，树不相同；
否则，递归比较左右子树是否相同。
代码：
1 /** 2 * Definition for binary tree 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 bool isSameTree(TreeNode *p, TreeNode *q) { 13 if(p == NULL && q == NULL) 14 return true; 15 if((p == NULL && q != NULL) ||(p != NULL && q == NULL)) 16 return false; 17 if(p->val != q->val) 18 return false; 19 return isSameTree(p->left,q->left) && isSameTree(p->right,q->right); 20 } 21 };
Java版本代码：
1 public class Solution { 2 public boolean isSameTree(TreeNode p, TreeNode q) { 3 int ispempty = p == null?0:1; 4 int isqempty = q == null?0:1; 5 if(ispempty != isqempty) 6 return false; 7 return isSameTreeHelper(p, q); 8 } 9 public boolean isSameTreeHelper(TreeNode p,TreeNode q){ 10 if(p == null && q == null) 11 return true; 12 if(p.val != q.val) 13 return false; 14 15 int pleftempty = p.left == null?0:1; 16 int qleftempty = q.left == null?0:1; 17 if(pleftempty != qleftempty) 18 return false; 19 if(isSameTreeHelper(p.left, q.left) == false) 20 return false; 21 22 int prightempty = p.right == null?0:1; 23 int qrightempty = q.right == null?0:1; 24 if(prightempty != qrightempty) 25 return false; 26 if(isSameTreeHelper(p.right, q.right) == false) 27 return false; 28 29 return true; 30 31 } 32 }
Java版本写复杂了=。=