面試題31. 棧的壓入、彈出序列

題目：

面試題31. 棧的壓入、彈出序列
946. 驗證棧序列

題解：

代碼：

import java.util.*;

public class 面試題31 {

    public static boolean validateStackSequences(int[] pushed, int[] popped) 
    {
        Stack<Integer> stack = new Stack<>();
        int k = 0;
        for(int i = 0; i < pushed.length; i++)
        {
            stack.push(pushed[i]); // pushed[i] 入棧
            while(!stack.empty() && stack.peek() == popped[k]) // 循環判斷與出棧
            {
                stack.pop();
                k++;
            }
        }
        if(stack.empty())
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    public static void main(String[] args) {
        int pushed1[] = { 1, 2, 3, 4, 5 };
        int popped1[] = { 4, 5, 3, 2, 1 };
        boolean res1 = validateStackSequences(pushed1, popped1);
        System.out.println(res1);

        int pushed2[] = { 1, 2, 3, 4, 5 };
        int popped2[] = { 4, 3, 5, 1, 2 };
        boolean res2 = validateStackSequences(pushed2, popped2);
        System.out.println(res2);
    }
}

參考：

1. 面試題31. 棧的壓入、彈出序列（模擬，清晰圖解）
2. 圖解 模擬入棧操作，貪心算法
3. 驗證棧序列