C#算法题三道
hihocoder微软在线测试帮助
2T 3T的题干
1. A+B问题
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
///在线测试
///A+B problem
namespace Ex01
{
class Program
{
static void Main(string[] args)
{
string line;
while ((line = Console.ReadLine()) != null)
{
string[] take = line.Split(' ');
Console.WriteLine(int.Parse(take[0]) + int.Parse(take[1]));
}
}
}
}
2. String Reorder
///微软2014实习生在线测试题目
///http://blog.csdn.net/huolei_blog/article/details/23554891
///T1：字符串排序
///http://blog.csdn.net/huolei_blog/article/details/23555167
添加using System.Collections;
static void Main1()//Main方法没参数也行。。。
{
string line;
while ((line = Console.ReadLine()) != null)
{
bool isLegal = true;
char[] input = line.ToArray();
ArrayList AL_input = new ArrayList();
for (int i = 0;isLegal && i < input.Length; i++)
{
if(input[i]>'z' || input[i]<'0' || (input[i]>'9' && input[i]<'a'))
{
isLegal = false;
Console.Write("<invalid input string>");
break;
}
AL_input.Add(input[i]);
}
//默认按照ascii码排序，符合题意。
AL_input.Sort();
//此处用AL_input是否为null判断会导致死循环
while (isLegal && AL_input.Count != 0)//遇到不合法的输入不必做处理。
{
ArrayList subSet = new ArrayList();
foreach (object i in AL_input)
{
if (!subSet.Contains(i))
{
subSet.Add(i);
//Console.WriteLine("subSet add {0}.", i);
}
}
foreach (object i in subSet)
{
Console.Write(i);
AL_input.Remove(i);
}
}
Console.WriteLine();
}
}
输出结果
/*输出结果 aabbccdd abcdabcd 007799aabbccddeeff113355zz 013579abcdefz013579abcdefz 1234.89898 .123489898 abcdefabcdefabcdefaaaaaaaaaaaaaabbbbbbbddddddee abcdefabcdefabcdefabdeabdeabdabdabdabdabaaaaaaa */ /*定义bool isLegal = true;之后的输出结果 aabbccdd abcdabcd 007799aabbccddeeff113355zz 013579abcdefz013579abcdefz 1234.89898 <invalid input string> abcdefabcdefabcdefaaaaaaaaaaaaaabbbbbbbddddddee abcdefabcdefabcdefabdeabdeabdabdabdabdabaaaaaaa */
3. K-th string（本方法对于稍大的输入值会陷入等待状态）
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections;
///T2：K-th string
namespace Ex01
{
/// <summary>
/// 使用强大的ArrayList和StringBuilder
/// </summary>
class T2_K_string
{
static void Main(string[] args)
{
int testCase = int.Parse(Console.ReadLine());
while (testCase-- > 0)
{
int n, m, k;
string line = Console.ReadLine();
string[] take = line.Split(' ');
n = int.Parse(take[0]);
m = int.Parse(take[1]);
k = int.Parse(take[2]);
//Console.WriteLine("{0} {1} {2}. ",n,m,k);
ArrayList al = new ArrayList();
int number = GetCombination(n + m, n);
//Console.WriteLine("number等于C (n+m) n");
while (al.Count < number)
{
string s = Creator(n, m);
if (!al.Contains(s)) al.Add(s);
}
al.Sort();
//Console.WriteLine("排序之后的顺序");
//foreach (string s in al)
//{
// Console.WriteLine(s);
//}
//Console.WriteLine("k={0} count={1}. 第k位的元素{2}", k, al.Count,al[k]);
if (k > al.Count) Console.WriteLine("Impossible");
else Console.WriteLine(al[k-1]);
}
}
/// <summary>
/// 计算组合数
/// </summary>
/// <param name="top">C的下标</param>
/// <param name="bottom">C的上标</param>
/// <returns>组合数的值</returns>
private static int GetCombination(int top,int bottom)
{
int[] _top = new int[top];
int[] _bottom = new int[bottom];
for (int i = 0; i < top; i++) _top[i] = i+1;
for (int i = 0; i < bottom; i++) _bottom[i] = i+1;
//given the anwer = x/y
int x, y; x=y=1;
for (int i = 0; i < _bottom.Length; i++)
{
y *= _bottom[i];
x *= _top[_top.Length -1 - i];
}
return x / y;
}
/// <summary>
/// 获取一个0和1组成的随机字符串
/// 计算机计算速度快，用随机字符串取完所有组合。
/// </summary>
/// <param name="n">字符串中0的个数</param>
/// <param name="m">字符串中1的个数</param>
/// <returns>随机字符串</returns>
public static string Creator(int n, int m)
{
/**Each test case is 3 integers separated by blank space:
* N, M(2 <= N + M <= 33 and N , M >= 0), K(1 <= K <= 1000000000).
* N stands for the number of ‘0’s,
* M stands for the number of ‘1’s,
* and K stands for the K-th of string in the set that needs to be printed as output.
*/
StringBuilder sb = new StringBuilder();
Random rand = new Random();
while (n > 0 && m > 0)
{
//以1/2的概率添加每一位
if (rand.Next(2) == 0)
{
sb.Append(0);
n--;
}
else
{
sb.Append(1);
m--;
}
}
if (n > 0)
{
while (n-- >0) sb.Append(0);
}
else if (m > 0)
{
while (m-- > 0) sb.Append(1);
}
//we got the anwer
return sb.ToString();
}
}
}
/*输出结果｛！！本算法导致数据大的时候算不出来｝
3
2 2 2
0101
2 2 7
Impossible
4 7 47
*/
4. 用递归求字符数组（即字符串）的全排列
/// 递归方法求字符串元素的全排列
http://www.dotblogs.com.tw/messboy000/archive/2014/02/15/144004.aspx
static void Main0(string[] args)
{
permute("", "123");
Console.ReadKey();
}
static void permute(string result, string now)
{
if (now == "")
{
Console.WriteLine(result);
}
else
{
for (int i = 0; i < now.Length; i++)
{
//Console.WriteLine("i={0}, now.Substring(i + 1)={1}.", i, now.Substring(i + 1));
permute(result + now[i], now.Substring(0, i) + now.Substring(i + 1));
}
}
}
/*递归过程主要使用这两个函数：
* Substring(int startIndex):子字符串从指定的字符位置startIndex到字符串结束。
* Substring(int startIndex, int length)：从startIndex开始长为length的子字符串。
* 如此就可以不断遍历，想象一棵递归树，那么其最左枝便是：
* (null,123)
* (1,23)
* (12,3)
* (123,null)这时输出。
*/
输出结果
/*加上注释之后的输出结果。 i=0, now.Substring(i + 1)=23 i=0, now.Substring(i + 1)=3. i=0, now.Substring(i + 1)=. 123 i=1, now.Substring(i + 1)=. i=0, now.Substring(i + 1)=. 132 i=1, now.Substring(i + 1)=3. i=0, now.Substring(i + 1)=3. i=0, now.Substring(i + 1)=. 213 i=1, now.Substring(i + 1)=. i=0, now.Substring(i + 1)=. 231 i=2, now.Substring(i + 1)=. i=0, now.Substring(i + 1)=2. i=0, now.Substring(i + 1)=. 312 i=1, now.Substring(i + 1)=. i=0, now.Substring(i + 1)=. 321 */ /*将123替换为abcd的输出结果。 abcd abdc acbd acdb adbc adcb bacd badc bcad bcda bdac bdca cabd cadb cbad cbda cdab cdba dabc dacb dbac dbca dcab dcba */
占位