Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
For example, this binary tree is symmetric:
1
/ \
2 2
/ \ / \
3 4 4 3
But the following is not:
1
/ \
2 2
\ \
3 3
采用递归的方式
#include <assert.h>
#include <stdlib.h>
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
};
int isAMirror(struct TreeNode *left, struct TreeNode *right) {
if(left==NULL && right==NULL)
return 1;
if(left==NULL || right==NULL)
return 0;
return (left->val == right->val) && isAMirror(left->left, right->right) && isAMirror(left->right, right->left);
}
int isSymmetric(struct TreeNode *root) {
if(root == NULL)
return 1;
return isAMirror(root->left, root->right);
}
int main() {
struct TreeNode *root = malloc(sizeof(struct TreeNode));
root->val = 1;
struct TreeNode *left = malloc(sizeof(struct TreeNode));
left->val = 2;
struct TreeNode *right = malloc(sizeof(struct TreeNode));
right->val = 3;
root->left = left;
root->right = right;
left->left = NULL;
left->right = NULL;
right->left = NULL;
right->right = NULL;
assert(isSymmetric(root) == 0);
return 0;
}
