232. Implement Queue using Stacks
2016-02-13 00:16
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class MyQueue {
// Push element x to the back of queue.
Stack<Integer> s1 = new Stack<>();
Stack<Integer> s2 = new Stack<>();
public void push(int x) {
s1.push(x);
}
// Removes the element from in front of queue.
public void pop() {
if(!s2.isEmpty())s2.pop();
else{
while(!s1.isEmpty()){
s2.push(s1.pop());
}
s2.pop();
}
/* if(!s2.isEmpty()) s2.pop();
else {
while(!s1.isEmpty()) s2.push(s1.pop());
s2.pop();
}*/
}
// Get the front element.
public int peek() {
if(!s2.isEmpty()) return s2.peek();
else {
while(!s1.isEmpty()) s2.push(s1.pop());
return s2.peek();
}
}
// Return whether the queue is empty.
public boolean empty() {
return s1.empty() && s2.empty();
}
}
// Push element x to the back of queue.
Stack<Integer> s1 = new Stack<>();
Stack<Integer> s2 = new Stack<>();
public void push(int x) {
s1.push(x);
}
// Removes the element from in front of queue.
public void pop() {
if(!s2.isEmpty())s2.pop();
else{
while(!s1.isEmpty()){
s2.push(s1.pop());
}
s2.pop();
}
/* if(!s2.isEmpty()) s2.pop();
else {
while(!s1.isEmpty()) s2.push(s1.pop());
s2.pop();
}*/
}
// Get the front element.
public int peek() {
if(!s2.isEmpty()) return s2.peek();
else {
while(!s1.isEmpty()) s2.push(s1.pop());
return s2.peek();
}
}
// Return whether the queue is empty.
public boolean empty() {
return s1.empty() && s2.empty();
}
}
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