57 lines
1.3 KiB
Markdown
57 lines
1.3 KiB
Markdown
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# 用栈实现队列 && 用队列实现栈
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## 用栈实现队列
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[Leetcode](https://leetcode.com/problems/implement-queue-using-stacks/)
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「输入栈」会把输入顺序颠倒；如果把「输入栈」的元素逐个弹出放到「输出栈」，再从「输出栈」弹出元素的时候，则可以负负得正，实现了先进先出。
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```cpp
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#include <stack>
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class MyQueue {
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public:
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std::stack<int> *inStack, *outStack;
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MyQueue() {
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inStack = new std::stack<int>;
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outStack = new std::stack<int>;
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}
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void transfer(void) {
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if (outStack->empty()) {
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while (!inStack->empty()) {
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outStack->push(inStack->top());
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inStack->pop();
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}
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}
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}
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void push(int x) { inStack->push(x); }
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int pop() {
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transfer();
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int val = outStack->top();
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outStack->pop();
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return val;
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}
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int peek() {
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transfer();
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return outStack->top();
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}
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bool empty() { return inStack->empty() && outStack->empty(); }
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};
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```
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## 用队列实现栈
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[Leetcode](https://leetcode.com/problems/implement-stack-using-queues/)
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一个队列为主队列，一个为辅助队列，当入栈操作时，我们先将主队列内容导入辅助队列，然后将入栈元素放入主队列队头位置，再将辅助队列内容，依次添加进主队列即可。
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```cpp
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```
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