KMP与Sunday算法

KMP的next函数有两种形式，一种是next[0]=-1的，另一种是next[0]=0的，这里采用了第二种。

分两个函数写成，1.求next；2.匹配。

求next和匹配的过程看上去有那么点点类似。上代码：

#include <iostream>#include <iterator>using namespace std;  // 求next函数void build_next(char * s,int *next)  {      int i=0,j=-1;  int n = strlen(s);    next[0]=-1;    while(i<n)      {          if(j==-1 || s[i]==s[j])          {              ++j;  ++i;next[i] = j;        }          else          {j = next[j];        }     }  }    // kmp  int KMP(char s[],char t[],int m,int n, int *next)   {      build_next(t, next);      int i=-1;      int j=-1;        while( i<m && j<n)      {          if(j==-1 || s[i]==t[j])          {              ++j;  ++i;        }          else          {j = next[j];        }    }  if(j<n)return -1;  else return i-n;}   // 求sunday的数组void getsun(char *s, int *sun){memset(sun,0,sizeof(int)*256);int n = strlen(s);int i;for(i=0;i<256;i++)sun[i] = n+1;for (i=0;i<n;i++){sun[s[i]] = n-i;}}// sunday算法int sunday(char s[],char t[],int m,int n, int *sun){int i=0,j=0;while(i<m && j<n){if(s[i] == t[j]){++j;++i;}else{j = 0;i = i - j + int(sun[s[i+n]]);}}if(j<n)return -1;else return i-j;}// 暴力搜索int bf(char s[],char t[],int m,int n, int *sun){int i=0,j=0;while( i<m && j<n ){if (s[i] == t[j] ){++i;++j;}else{i = i-j+1;j = 0;}}if(j<n)return -1;elsereturn i-j;}int next1[20];int main(){char s[] = "abacvhsvababca";char t[] = "ababc";int n=strlen(t);int m=strlen(s);// kmpint index = KMP(s,t,m,n,next1);cout<<"KMP:"<<endl<<index<<" "<<(s+index)<<endl;copy(next1,next1+n,ostream_iterator<int>(cout," "));cout<<endl;// sundayint *sun = new int[256];getsun(t,sun);cout<<endl<<"sunday:"<<endl;//copy(sun,sun+256,ostream_iterator<int>(cout," "));int ii = sunday(s,t,m,n,sun);cout<<endl<<"sunday:"<<endl<<(s+ii)<<endl;delete []sun;cout<<"暴力搜索:"<<endl;cout<<(s+bf(s,t,m,n,next1))<<endl;return 0;}