leetcode/notes/src/impl_stack_queue.md
Sainnhe Park 587076ab11
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Add impl stack queue
2022-12-06 17:24:52 +08:00

1.3 KiB

用栈实现队列 && 用队列实现栈

用栈实现队列

Leetcode

「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。

#include <stack>

class MyQueue {
 public:
  std::stack<int> *inStack, *outStack;

  MyQueue() {
    inStack = new std::stack<int>;
    outStack = new std::stack<int>;
  }

  void transfer(void) {
    if (outStack->empty()) {
      while (!inStack->empty()) {
        outStack->push(inStack->top());
        inStack->pop();
      }
    }
  }

  void push(int x) { inStack->push(x); }

  int pop() {
    transfer();
    int val = outStack->top();
    outStack->pop();
    return val;
  }

  int peek() {
    transfer();
    return outStack->top();
  }

  bool empty() { return inStack->empty() && outStack->empty(); }
};

用队列实现栈

Leetcode

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。