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Copy pathqueue2stack.cpp
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78 lines (72 loc) · 1.39 KB
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// 用队列实现栈
// 思路 用两个队列
#include <iostream>
#include <queue>
#include <algorithm>
using namespace std;
class MyStack{
private:
queue<int> q1;
queue<int> q2;
public:
MyStack(){
}
void push(int obj){
q1.push(obj);
}
void pop(){
if (q1.empty()){
cerr << "pop-->your stack is empty" << endl;
}
else if (q1.size() == 1){
q1.pop();
}
else{
int size = q1.size();
//!这里将for循环条件换成for (int i = 0; i < q1.size() - 1; i++)
//!则当长度为20时，循环只会进行9次,原因是循环体内有pop()操作，这会改变q1.size()的值
for (int i = 0; i < size - 1; i++){
int tmp = q1.front();
q1.pop();
q2.push(tmp);
}
q1.pop();
// 这里也可以直接将q1和q2的引用交换一下
//!此处与上文同，需记录q2的长度
int size2 = q2.size();
for (int i = 0; i < size2; i++){
int tmp = q2.front();
q2.pop();
q1.push(tmp);
}
}
}
int top(){
if (q1.empty()){
cerr << "top-->your stack is empty" << endl;
return NULL;
}
else{
return q1.back();
}
}
int size(){
return q1.size();
}
};
int main(){
MyStack s1;
cout << "the content:" << endl;
for (int i = 0; i < 20; i++){
s1.push(i);
cout << s1.top() << " ";
}
cout << endl;
cout << "pop:" << endl;
for (int i = 0; i < 20; i++){
cout << s1.top() << " ";
s1.pop();
}
system("pause");
return 0;
}