2014
11-19

# LeetCode-Same Tree[二叉树]

### Same Tree

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.

// LeetCode, Same Tree
// 递归版，时间复杂度O(n)，空间复杂度O(logn)
class Solution {
public:
bool isSameTree(TreeNode *p, TreeNode *q) {
if (!p && !q) return true;   // 终止条件
if (!p || !q) return false;  // 剪枝
return p->val == q->val      // 三方合并
&& isSameTree(p->left, q->left)
&& isSameTree(p->right, q->right);
}
};


// LeetCode, Same Tree
// 迭代版，时间复杂度O(n)，空间复杂度O(logn)
class Solution {
public:
bool isSameTree(TreeNode *p, TreeNode *q) {
stack<TreeNode*> s;
s.push(p);
s.push(q);

while(!s.empty()) {
p = s.top(); s.pop();
q = s.top(); s.pop();

if (!p && !q) continue;
if (!p || !q) return false;
if (p->val != q->val) return false;

s.push(p->left);
s.push(q->left);

s.push(p->right);
s.push(q->right);
}
return true;
}
};


Java代码:

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if(p == null && q == null) return true;
if(p == null || q == null) return false;
if(p.val != q.val) return false;
return isSameTree(p.left,q.left) && isSameTree(p.right,q.right);
}
}

Symmetric Tree

1. 漂亮。佩服。
P.S. unsigned 应该去掉。换行符是n 不是/n
还可以稍微优化一下，
int main() {
int m,n,ai,aj,bi,bj,ak,bk;
while (scanf("%d%d",&m,&n)!=EOF) {
ai = sqrt(m-1);
bi = sqrt(n-1);
aj = (m-ai*ai-1)>>1;
bj = (n-bi*bi-1)>>1;
ak = ((ai+1)*(ai+1)-m)>>1;
bk = ((bi+1)*(bi+1)-n)>>1;
printf("%dn",abs(ai-bi)+abs(aj-bj)+abs(ak-bk));
}
}