// 面试题31:栈的压入、弹出序列 // 题目:输入两个整数序列,第一个序列表示栈的压入顺序,请判断第二个序列是 // 否为该栈的弹出顺序。假设压入栈的所有数字均不相等。例如序列1、2、3、4、 // 5是某栈的压栈序列,序列4、5、3、2、1是该压栈序列对应的一个弹出序列,但 // 4、3、5、1、2就不可能是该压栈序列的弹出序列。 #include <iostream> #include <stack> bool IsPopOrder(const int* pPush, const int* pPop, int nLength) { bool bPossible = false; if (pPush != nullptr && pPop != nullptr && nLength > 0) { const int* pNextPush = pPush; const int* pNextPop = pPop; std::stack<int> stackData; while (pNextPop - pPop < nLength) { // 当辅助栈的栈顶元素不是要弹出的元素 // 先压入一些数字入栈 while (stackData.empty() || stackData.top() != *pNextPop) { // 如果所有数字都压入辅助栈了,退出循环 if (pNextPush - pPush == nLength) break; stackData.push(*pNextPush); pNextPush++; } if (stackData.top() != *pNextPop)//完了,不匹配 break; stackData.pop();//弹出这个匹配的 pNextPop++;//检测下一个要pop的 } if (stackData.empty() && pNextPop - pPop == nLength)//检测条件 bPossible = true; } return bPossible; } // ====================测试代码==================== void Test(const char* testName, const int* pPush, const int* pPop, int nLength, bool expected) { if (testName != nullptr) printf("%s begins: ", testName); if (IsPopOrder(pPush, pPop, nLength) == expected) printf("Passed. "); else printf("failed. "); } void Test1() { const int nLength = 5; int push[nLength] = { 1, 2, 3, 4, 5 }; int pop[nLength] = { 4, 5, 3, 2, 1 }; Test("Test1", push, pop, nLength, true); } void Test2() { const int nLength = 5; int push[nLength] = { 1, 2, 3, 4, 5 }; int pop[nLength] = { 3, 5, 4, 2, 1 }; Test("Test2", push, pop, nLength, true); } void Test3() { const int nLength = 5; int push[nLength] = { 1, 2, 3, 4, 5 }; int pop[nLength] = { 4, 3, 5, 1, 2 }; Test("Test3", push, pop, nLength, false); } void Test4() { const int nLength = 5; int push[nLength] = { 1, 2, 3, 4, 5 }; int pop[nLength] = { 3, 5, 4, 1, 2 }; Test("Test4", push, pop, nLength, false); } // push和pop序列只有一个数字 void Test5() { const int nLength = 1; int push[nLength] = { 1 }; int pop[nLength] = { 2 }; Test("Test5", push, pop, nLength, false); } void Test6() { const int nLength = 1; int push[nLength] = { 1 }; int pop[nLength] = { 1 }; Test("Test6", push, pop, nLength, true); } void Test7() { Test("Test7", nullptr, nullptr, 0, false); } int main(int argc, char* argv[]) { Test1(); Test2(); Test3(); Test4(); Test5(); Test6(); Test7(); system("pause"); return 0; }