题目1512：用两个栈实现队列

题目描述：用两个栈来实现一个队列，完成队列的Push和Pop操作。队列中的元素为int类型。输入：每个输入文件包含一个测试样例。对于每个测试样例，第一行输入一个n(1<=n<=100000)，代表队列操作的个数。接下来的n行，每行输入一个队列操作：1. PUSH X 向队列中push一个整数x(x>=0)2. POP 从队列中pop一个数。输出：对应每个测试案例，打印所有pop操作中从队列pop中的数字。如果执行pop操作时，队列为空，则打印-1。样例输入：

3
PUSH 10
POP
POP

样例输出：

10
-1

/**题目1512：用两个栈实现队列* */#include <iostream>#include <stack>#include <cstdio>#include <cstring>using namespace std;template <typename _type>class MyQueue {public :MyQueue ()  {}~MyQueue () {while (!org.empty())org.pop();while (!cpy.empty())cpy.pop();}void push (const _type& val) {org.push (val);}const _type pop () {if (cpy.empty ())  {if (org.empty())return static_cast<_type>(-1);else {while (!org.empty()) {cpy.push(org.top());org.pop();}}}const _type res_val = cpy.top();cpy.pop();return res_val;}private :stack<_type> org;stack<_type> cpy;};int main () {MyQueue<int> q;const char * PUSH = "PUSH";const char * POP  = "POP";char cmd[20];int n, val;while (scanf ("%d", &n) == 1) {if (n < 1 )continue;for ( int i = 0; i < n; ++i ) {scanf ("%s", cmd) ;if (strcmp(cmd, PUSH) == 0) {scanf ("%d", &val) ;q.push(val);}else if (strcmp(cmd, POP) == 0) {printf ("%d\n", q.pop());}//cout << "cmd :" << cmd << "\tval : " << val << endl;}}return 0;}/**************************************************************Problem: 1512User: 小康师傅Language: C++Result: AcceptedTime:70 msMemory:1656 kb****************************************************************/

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