Implementation of longest common sub-sequence in c

#include<stdio.h>
#include<stdlib.h>
int max(int a,int b){return (a>b)?a:b;}
char *x, *y;
int lcs(int i,int j)
 {
  if(i==0||j==0)return 0;
  else if(i>0&&j>0&&x[i]==y[j]) return lcs(i-1,j-1)+1;
  else if(i>0&&j>0&&x[i]!=y[j]) return max(lcs(i-1,j),lcs(i,j-1));
}
int main()
{int n=10,m=5;

 x=(char *)malloc(n*sizeof(char ));
 y=(char *)malloc(m*sizeof(char ));
 gets(x);
 gets(y);
 //sizeof longest common subsequence among first n letters of x and first m letters of y
 printf("%d",lcs(n,m));
return 0;
}

Program for String Matching with Finite Automata in C

#include <stdio.h>
#include <stdlib.h>
char * prefix(char * c,int start, int end,int size)
{   int i;
    char *temp=(char *)malloc(size*sizeof(char));
    for(i=0;i<size;i++)
       temp[i]=c[start++];
    return temp;
}
char * suffix(char * c,int start, int end,int size)
{   int i,j;
    char *temp=(char *)malloc(size*sizeof(char));
    for(j=0,i=end-size+1;i<=end;i++,j++)
       temp[j]=c[i];
    return temp;
}
int match(char * a, char *b)
{  int i=0;
    while(a[i]!='\0')
     {
if(a[i]!=b[i])
 return 0;
i++;
     }
    return 1;
}
int sigma(char * t , char * p ,int i)
{
  int j,v=0;
  for(j=0;p[j]!='\0';j++)
     if(match(suffix(t,0,i,j+1),prefix(p,0,j,j+1)))
v=j+1;
  return v;
}
int main()
{  char a[]="dfhghjgfjschhscgchgfbgfsgfjh";
   char b[]="jhgfj";
   printf("%d\n",sigma(a,b,8));
   
 
}

Implmentation of Rabin-Karp Algorithm in c

#include <stdio.h>
#include<stdlib.h>
int hash (char * a,int s,int t)
{ int h=0;
    for(;s<=t;s++)
        h+=a[s];
       return h;
}
int match(char * a,int a1,int a2,char * b, int b1,int b2)
{  
    for(;a1<=a2,b1<=b2;a1++,b1++)
       { if(a[a1]!=b[b1])
           return 0;
       }
       return 1;
}   
   

void rk(char*a,char *b,int as,int bs)
{ 
   int ph=hash(b,0,bs-1),i;
   for(i=0;i<(as-bs+1);i++)
    { if(hash(a,i,i+bs-1)==ph)
        if(match(a,i,i+bs-1,b,0,bs-1))
      { printf("  match for < %s > found at position : %d ",b,i+1);}
    }
        
    
}
void main()
{  
 char t[]="abcdefghijklmnopqrstuvwxyz";
 char p[]="klmnop";
    int st=sizeof(t)-1;
    int  sp=sizeof(p)-1;
    rk(t,p,st,sp);
    
    
}

Simple string matching algorithm to find position of a pattern in a given string without using any string function in C

#include<stdio.h>
#include<stdlib.h>
void main()
{ int i=0,j,count;
  char string[]={"kfhisdcodesoecodeupzz"};
  char pattern[]={"code"};
 
 
  for(i=0;i<sizeof(string)-1;i++)
     {
     
       if(string[i]==pattern[0])
         { count =1;

           for(j=1;j<sizeof(pattern)-1;j++)
              {
                if(pattern[j]==string[i+j])
                   count++;
                else break;
              }

         if(count==(sizeof(pattern)-1))
         printf("\none match at position : %d ",i);
           
         }
     
     }
printf("\n");
}