• [LeetCode] Implement Queue using Stacks


    A classic interview question. This link has a nice explanation of the idea using two stacks and its amortized time complexity.

    I use the same idea in my code, which is as follows.

     1 class Queue {
     2 public:
     3     // Push element x to the back of queue.
     4     void push(int x) {
     5         stack1.push(x);
     6     }
     7 
     8     // Removes the element from in front of queue.
     9     void pop(void) {
    10         if (stack2.empty()) {
    11             while (!stack1.empty()) {
    12                 int elem = stack1.top();
    13                 stack1.pop();
    14                 stack2.push(elem);
    15             }
    16         }
    17         stack2.pop();
    18     }
    19 
    20     // Get the front element.
    21     int peek(void) {
    22         if (stack2.empty()) {
    23             while (!stack1.empty()) {
    24                 int elem = stack1.top();
    25                 stack1.pop();
    26                 stack2.push(elem);
    27             }
    28         }
    29         return stack2.top();
    30     }
    31 
    32     // Return whether the queue is empty.
    33     bool empty(void) {
    34         return stack1.empty() && stack2.empty();
    35     }
    36 private:
    37     stack<int> stack1;
    38     stack<int> stack2;
    39 };
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  • 原文地址:https://www.cnblogs.com/jcliBlogger/p/4626552.html
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