演算法面試題

最近到某公司面試後，被問到2個關於演算法的題目：

1.最大子段和（一個經典的動態規划算法求解題）

2.已知資料類型棧，請實現隊列。

 

代碼如下：

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
class Program
    {
static void Main(string[] args)
        {
int[] a = new int[] { -1, 3, -5, 1, 8, -7, 8, -5, 6, -5, -6 };
            Console.WriteLine("最大子段和是："+MaxSum(a));


            Queue q = new Queue();
for (int i = 0; i < 10; i++) q.Push(i);
for (int i = 0; i < 11; i++) Console.WriteLine(q.Pop());
for (int i = 0; i < 10; i++) q.Push(i);
for (int i = 0; i < 11; i++) Console.WriteLine(q.Pop());
        }

/// <summary>
/// 最大子段和
/// </summary>
/// <param name="array"></param>
/// <returns></returns>
        static int MaxSum(int[] array)
        {
int b=0;
int sum=0;
for (int i = 0; i < array.Length; i++)
            {
if (b > 0) b += array[i];
else b = array[i];
if (sum < b) sum = b;
            }
return sum;

        }
    }

/// <summary>
/// 自訂隊列
/// </summary>
    class Queue
    {
        Stack<int> sa = new Stack<int>();
        Stack<int> sb = new Stack<int>();

/// <summary>
/// 將元素插入隊列
/// </summary>
/// <param name="item"></param>
        public void Push(int item)
        {
            sa.Push(item);
        }

/// <summary>
/// 從隊列刪除並返回一個元素
/// </summary>
/// <returns></returns>
        public int? Pop()
        {
if (IsEmpty()) return null;

if (sb.Count == 0)
            {
while (sa.Count > 0) sb.Push(sa.Pop());
return sb.Pop();
            }
else return sb.Pop();
        }

/// <summary>
/// 判斷隊列是否為空白
/// </summary>
/// <returns></returns>
        public bool IsEmpty()
        {
if (sa.Count == 0 && sb.Count == 0) return true;
else return false;
        }


    }
}