program2-strings

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
char str[100], pat[100], rep[100];
int slen(char *s)
{
    int length=0;
    while(s[length++]!='\0'){}
    return (length-1);
}
void findAndReplace()
{
    int s, p, r, found=0, i, temp, diff=abs(slen(pat)-slen(rep));
    for(s=0;str[s]!='\0';s++)
    {
        temp=s;
        for(p=0;pat[p]!='\0';)
        {
            if(str[s]==pat[p])
            {
                s++;
                p++;
            }
            else
                break;
            if(pat[p]=='\0')
            {
                found=1;
                if(slen(pat)<slen(rep))
                {
                    for(s=slen(str);s>=temp;s--)
                        str[s+diff]=str[s];
                    for(s=temp,r=0;rep[r]!='\0';s++,r++)
                        str[s]=rep[r];
                }
                else if(slen(rep)<slen(pat))
                {
                    for(s=temp+slen(rep);s<=slen(str)-diff;s++)
                        str[s]=str[s+diff];
                    for(s=temp,r=0;rep[r]!='\0';s++,r++)
                        str[s]=rep[r];
                }
                else
                {
                    for(s=temp,r=0;rep[r]!='\0';s++,r++)
                        str[s]=rep[r];
                }
            }
        }
        s=temp;
    }
    if(found)
        printf("\nThe Resultant String is: %s\n",str);
    else
        printf("\nPattern String not found\n");
}
int main()
{
    printf("\nEnter the Main String: ");
    gets(str);
    printf("\nEnter the Pattern String: ");
    gets(pat);
    printf("\nEnter the Replacement String: ");
    gets(rep);
    findAndReplace();
    return 0;
}