- 利用一个额外栈来保存当前值最小值
- 压栈时,额外栈只存入不小于自己栈顶的值
- 出栈时,额外栈只在存值栈等于自己栈顶值时出栈
import java.util.Stack; public class Solution { Stack<Integer> stack = new Stack(); Stack<Integer> minStack = new Stack(); public void push(int node) { stack.push(node); // 压入最小值 if(minStack.empty() || node <= minStack.peek()) { minStack.push(node); } } public void pop() { // 最小栈在相等时出栈 if(!stack.empty() && stack.peek() == minStack.peek()) { minStack.pop(); } stack.pop(); } public int top() { return stack.peek(); } public int min() { return minStack.peek(); } }