Add C++ solution for leetcode 232.

Author: Bruce Yang

91algo/daily/day5[2021-09-14] leetcode232-implement-queue-using-stacks_two_stacks.cpp

@@ -0,0 +1,66 @@
+#include<stack>
+#include<algorithm>
+#include<iostream>
+using namespace std;
+
+class MyQueue {
+    stack<int> s1, s2;
+    int front;
+    
+public:
+    /** Initialize your data structure here. */
+    MyQueue() {}
+    
+    /** Push element x to the back of queue. */
+    void push(int x) {
+        if (s1.empty())
+            front = x;
+        
+        s1.push(x);
+    }
+
+    /** Removes the element from in front of queue and returns that element. */
+    int pop() {
+        if (s2.empty())
+        {
+            while (!s1.empty())
+            { /* 把s1中的元素全部移到s2中 */
+                s2.push(s1.top());
+                s1.pop();
+            }
+        }
+        int res = s2.top();
+        s2.pop();
+
+        return res;
+    }
+
+    /** Get the front element. */
+    int peek() {
+        if (!s2.empty())
+            return s2.top();
+
+        return front;
+    }
+
+    /** Returns whether the queue is empty. */
+    bool empty() {
+        return s1.empty() && s2.empty();
+    }
+};
+
+// Test
+int main()
+{
+    MyQueue* q = new MyQueue();
+    q->push(1);
+    q->push(2);
+    int val = q->peek();
+    cout << val << endl;
+    int val2 = q->pop();  // return 1, queue is [2]
+    cout << val2 << endl;       
+    bool isEmpty = q->empty();
+    cout << (isEmpty ? "true" : "false") << endl;
+
+    return 0;
+}

cpp-leetcode/leetcode232-implement-queue-using-stacks_two_stacks.cpp

@@ -0,0 +1,66 @@
+#include<stack>
+#include<algorithm>
+#include<iostream>
+using namespace std;
+
+class MyQueue {
+    stack<int> s1, s2;
+    int front;
+    
+public:
+    /** Initialize your data structure here. */
+    MyQueue() {}
+    
+    /** Push element x to the back of queue. */
+    void push(int x) {
+        if (s1.empty())
+            front = x;
+        
+        s1.push(x);
+    }
+
+    /** Removes the element from in front of queue and returns that element. */
+    int pop() {
+        if (s2.empty())
+        {
+            while (!s1.empty())
+            { /* 把s1中的元素全部移到s2中 */
+                s2.push(s1.top());
+                s1.pop();
+            }
+        }
+        int res = s2.top();
+        s2.pop();
+
+        return res;
+    }
+
+    /** Get the front element. */
+    int peek() {
+        if (!s2.empty())
+            return s2.top();
+
+        return front;
+    }
+
+    /** Returns whether the queue is empty. */
+    bool empty() {
+        return s1.empty() && s2.empty();
+    }
+};
+
+// Test
+int main()
+{
+    MyQueue* q = new MyQueue();
+    q->push(1);
+    q->push(2);
+    int val = q->peek();
+    cout << val << endl;
+    int val2 = q->pop();  // return 1, queue is [2]
+    cout << val2 << endl;       
+    bool isEmpty = q->empty();
+    cout << (isEmpty ? "true" : "false") << endl;
+
+    return 0;
+}