C#之KMF算法

来源：互联网发布：打印纸品牌知乎编辑：程序博客网时间：2024/05/29 14:49
using System;using System.Text;using System.IO;namespace KMP{    class Kmp    {        public int[] next;        public string mainStr;//主串          public string modeStr;//模式串          public Kmp(string ms)        {            next = new int[ms.Length];            next[0] = -1;            next[1] = 0;        }        public void GetNext()  //获取模式串的next数组          {            for (int j = 2; j < modeStr.Length; j++)            {                next[j] = 0;                for (int k = 1; k < j; k++)                {                    string s1 = "";                    string s2 = "";                    for (int i = 0; i <= k; i++)                    {                        s1 += modeStr[i];                        s2 += modeStr[j - k];                        if (s1 == s2)                        {                            next[j] = next[j] > k ? next[j] : k;                        }                    }                }            }        }        public void GetNextval()  //改进的kmp算法，即修改next          {            for (int i = 2; i < next.Length; i++)            {                while (true)                {                    if (next[i] != -1 && modeStr[i] == modeStr[next[i]])                    {                        next[i] = next[next[i]];                    }                    else                    {                        break;                    }                }            }        }    }    class Program    {        static void Main()        {            string mainPath = @"F://test.txt";  //主串所在文件              string modePath = @"F://test1.txt"; //模式串所在文件              StreamReader sr = new StreamReader(mainPath, Encoding.Default);            string mainSt = ""; //用来存放主串              string s;            while ((s = sr.ReadLine()) != null)            {                mainSt += s;            }            sr = new StreamReader(modePath, Encoding.Default);            string modeStr = "";  //用来存放模式串              while ((s = sr.ReadLine()) != null)            {                modeStr += s;            }            Kmp kmp = new Kmp(modeStr);  //创建一个kmp对象              kmp.modeStr = modeStr;   //将读取到的模式串副歌相应的变量              kmp.mainStr = mainSt;            kmp.GetNext();   //获取模式串的next内容              kmp.GetNextval();//修改next的内容            for (int i = 0; i < kmp.next.Length; i++)             {                 Console.WriteLine(kmp.next[i]);             }            for (int i = 0, j = 0; i < modeStr.Length && j < mainSt.Length; j++)            {                if (modeStr[i] == mainSt[j])  //判断两个字符是否相等                  {                    if (i == modeStr.Length - 1)  //模式串的最后一个字符匹配成功                      {                        Console.WriteLine("在{0}处匹配成功", j - modeStr.Length);                        break;                    }                    i++;                    continue;                }                else if (j == mainSt.Length - 1)  //已经到达主串的最后一个字符                  {                    Console.WriteLine("匹配失败");                }                else if (kmp.next[i] == -1)                {                    i = kmp.next[i] + 1; //i=next[i]=-1修改为i=i+1=0;                  }                else                {                    i = kmp.next[i];                }            }        }    }}
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