155 最小栈

  1. class MinStack {
  2.     private Deque<Integer> stack;
  3.     private Deque<Integer> minStack;
  5.     /** initialize your data structure here. */
  6.     public MinStack() {
  7.         stack = new LinkedList<Integer>();
  8.         minStack = new LinkedList<Integer>();
  9.     }
  11.     public void push(int x) {
  12.         stack.push(x);
  13.         if (minStack.isEmpty() || x < minStack.peek())
  14.             minStack.push(x);
  15.         else 
  16.             minStack.push(minStack.peek());
  17.     }
  19.     public void pop() {
  20.         minStack.pop();
  21.         stack.pop();
  22.     }
  24.     public int top() {
  25.         return stack.peek();
  26.     }
  28.     public int getMin() {
  29.         return minStack.peek();
  30.     }
  31. }
  33. /**
  34.  * Your MinStack object will be instantiated and called as such:
  35.  * MinStack obj = new MinStack();
  36.  * obj.push(x);
  37.  * obj.pop();
  38.  * int param_3 = obj.top();
  39.  * int param_4 = obj.getMin();
  40.  */