225.用队列实现栈
题目链接
class MyStack {
public:
/** Initialize your data structure here. */
deque<int>mq;
int tp;
MyStack() {
}
/** Push element x onto stack. */
void push(int x) {
mq.emplace_back(x);
tp = x;
}
/** Removes the element on top of the stack and returns that element. */
int pop() {
int q = mq.size()-1;
while(q--){
tp = mq.front();
mq.emplace_back(mq.front());
mq.pop_front();
}
int ret = mq.front();
mq.pop_front();
return ret;
}
/** Get the top element. */
int top() {
return tp;
}
/** Returns whether the stack is empty. */
bool empty() {
return mq.empty();
}
};
/**
* Your MyStack object will be instantiated and called as such:
* MyStack* obj = new MyStack();
* obj->push(x);
* int param_2 = obj->pop();
* int param_3 = obj->top();
* bool param_4 = obj->empty();
*/
226.翻转二叉树
题目链接
class Solution {
public:
TreeNode* invertTree(TreeNode* root) {
if(root == NULL) return NULL;
invertTree(root->left);
invertTree(root->right);
swap(root->left,root->right);
return root;
}
};