algorithm-class/体系学习班/class03/Code05_GetMinStack.java

package class03;

import java.util.Stack;

public class Code05_GetMinStack {

	public static class MyStack1 {
		private Stack<Integer> stackData;
		private Stack<Integer> stackMin;

		public MyStack1() {
			stackData = new Stack<Integer>();
			stackMin = new Stack<Integer>();
		}

		public void push(int newNum) {
			if (stackMin.isEmpty() || newNum <= this.getmin()) {
				stackMin.push(newNum);
			}
			stackData.push(newNum);
		}

		public int pop() {
			if (stackData.isEmpty()) {
				throw new RuntimeException("Your stack is empty.");
			}
			int value = stackData.pop();
			if (value == getmin()) {
				stackMin.pop();
			}
			return value;
		}

		public int getmin() {
			if (stackMin.isEmpty()) {
				throw new RuntimeException("Your stack is empty.");
			}
			return stackMin.peek();
		}
	}

	public static class MyStack2 {
		private Stack<Integer> stackData;
		private Stack<Integer> stackMin;

		public MyStack2() {
			stackData = new Stack<Integer>();
			stackMin = new Stack<Integer>();
		}

		public void push(int newNum) {
			if (stackMin.isEmpty() || newNum < getmin()) {
				stackMin.push(newNum);
			} else {
				stackMin.push(stackMin.peek());
			}
			stackData.push(newNum);
		}

		public int pop() {
			if (stackData.isEmpty()) {
				throw new RuntimeException("Your stack is empty.");
			}
			stackMin.pop();
			return stackData.pop();
		}

		public int getmin() {
			if (stackMin.isEmpty()) {
				throw new RuntimeException("Your stack is empty.");
			}
			return stackMin.peek();
		}
	}

	public static void main(String[] args) {
		MyStack1 stack1 = new MyStack1();
		stack1.push(3);
		System.out.println(stack1.getmin());
		stack1.push(4);
		System.out.println(stack1.getmin());
		stack1.push(1);
		System.out.println(stack1.getmin());
		System.out.println(stack1.pop());
		System.out.println(stack1.getmin());

		System.out.println("=============");

		MyStack2 stack2 = new MyStack2();
		stack2.push(3);
		System.out.println(stack2.getmin());
		stack2.push(4);
		System.out.println(stack2.getmin());
		stack2.push(1);
		System.out.println(stack2.getmin());
		System.out.println(stack2.pop());
		System.out.println(stack2.getmin());
	}

}