解题思路:
辅助栈
class MinStack {
private Stack<Integer> stack;
private Stack<Integer> min_stack;
public MinStack() {
stack = new Stack<>();
min_stack = new Stack<>();
}
public void push(int val) {
stack.push(val);
if (min_stack.isEmpty() || val <= min_stack.peek())
min_stack.push(val);
}
public void pop() {
if (stack.pop().equals(min_stack.peek()))
min_stack.pop();
}
public int top() {
return stack.peek();
}
public int getMin() {
return min_stack.peek();
}
}