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LeetCode(剑指 Offer)- 09. 用两个栈实现队列


题目链接:​​点击打开链接​​

题目大意:略。

解题思路:略。

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AC 代码

  • Java
// 解决方案(1)
class CQueue {

private final Stack<Integer> stack1 = new Stack<>();
private final Stack<Integer> stack2 = new Stack<>();

public CQueue() {

}

public void appendTail(int value) {
stack1.push(value);
}

public int deleteHead() {
if (stack2.isEmpty()) {
while (!stack1.isEmpty()) {
stack2.push(stack1.pop());
}

if (stack2.isEmpty()) {
return -1;
}

}
return stack2.pop();
}
}

// 解决方案(2)
class CQueue {
LinkedList<Integer> A, B;
public CQueue() {
A = new LinkedList<Integer>();
B = new LinkedList<Integer>();
}
public void appendTail(int value) {
A.addLast(value);
}
public int deleteHead() {
if(!B.isEmpty()) return B.removeLast();
if(A.isEmpty()) return -1;
while(!A.isEmpty())
B.addLast(A.removeLast());
return B.removeLast();
}
}

/**
* Your CQueue object will be instantiated and called as such:
* CQueue obj = new CQueue();
* obj.appendTail(value);
* int param_2 = obj.deleteHead();
*/
  • C++
class CQueue {
public:
stack<int> A, B;
CQueue() {}
void appendTail(int value) {
A.push(value);
}
int deleteHead() {
if(!B.empty()) {
int tmp = B.top();
B.pop();
return tmp;
}
if(A.empty()) return -1;
while(!A.empty()) {
int tmp = A.top();
A.pop();
B.push(tmp);
}
int tmp = B.top();
B.pop();
return tmp;
}
};


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