Difficulty:: Easy
Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
- push(x) – Push element x onto stack.
- pop() – Removes the element on top of the stack.
- top() – Get the top element.
- getMin() – Retrieve the minimum element in the stack.
Example:
1
2
3
4
5
6
7
8
| MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); --> Returns -3.
minStack.pop();
minStack.top(); --> Returns 0.
minStack.getMin(); --> Returns -2.
|
Solution
Language: Java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
| class MinStack {
Deque<Integer> s1, s2;
public MinStack() {
s1 = new ArrayDeque<>();
s2 = new ArrayDeque<>();
}
public void push(int x) {
s1.push(x);
if (s2.size() == 0) {
s2.push(x);
} else {
if (s2.peek() > x) {
s2.push(x);
} else {
s2.push(s2.peek());
}
}
}
public void pop() {
s1.pop();
s2.pop();
}
public int top() {
return s1.peek();
}
public int getMin() {
return s2.peek();
}
}
|