155. Min Stack

Version #2 One Stack[TODO]


Version #1 Two Stacks
二刷
class MinStack {
    private Stack<Integer> stack;
    private Stack<Integer> minStack;
    /** initialize your data structure here. */
    public MinStack() {
        stack = new Stack<>();
        minStack = new Stack<>();
    }
 
    public void push(int x) {
        stack.push(x);
        if (minStack.isEmpty() || x < minStack.peek()) {
            minStack.push(x);
        } else {
            minStack.push(minStack.peek());
        }
    }
 
    public void pop() {
        stack.pop();
        minStack.pop();
    }
 
    public int top() {
        return stack.peek();
    }
 
    public int getMin() {
        return minStack.peek();
    }
}

一刷
public class MinStack {

    private Stack<Integer> minStack;

    private Stack<Integer> numStack;

    /** initialize your data structure here. */

    public MinStack() {

        minStack = new Stack<Integer>();

        numStack = new Stack<Integer>();

    }

    

    public void push(int x) {

        numStack.push(x);

        if (minStack.isEmpty() || x <= minStack.peek()) minStack.push(x);

    }

    

    public void pop() {

        if (numStack.isEmpty()) return;

        int num = numStack.pop();

        if (minStack.peek() == num) minStack.pop();

    }

    

    public int top() {

        if (numStack.isEmpty()) return Integer.MIN_VALUE;

        return numStack.peek();

    }

    

    public int getMin() {

        return minStack.peek();

    }

}

/**

 * Your MinStack object will be instantiated and called as such:

 * MinStack obj = new MinStack();

 * obj.push(x);

 * obj.pop();

 * int param_3 = obj.top();

 * int param_4 = obj.getMin();

 */