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剑指 Offer 09. 用两个栈实现队列

眼君 2022-01-09 阅读 99

剑指 Offer 09. 用两个栈实现队列 - 力扣(LeetCode) (leetcode-cn.com)

class CQueue {
public:
    stack<int> s1;
    stack<int>s2;
    CQueue() {
      s1.push(-1);
      s2.push(-1);
    }
    
    void appendTail(int value) {
        s1.push(value);
    }
    
    int deleteHead() {
        int res;
        if(s2.top()!=-1){
            res=s2.top();
            s2.pop();
            return res;
        }
        else{
            while(s1.top()!=-1){
                s2.push(s1.top());
                s1.pop();
            }
            if(s2.top()!=-1){
                res=s2.top();
                s2.pop();
                return res;
            }
            else return -1;
        }

    }
};

/**
 * Your CQueue object will be instantiated and called as such:
 * CQueue* obj = new CQueue();
 * obj->appendTail(value);
 * int param_2 = obj->deleteHead();
 */
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