/* A case-sensitive string replacement program
The Basic principle behind this program depends upon three cases
Case 1: If replacement string equals to 'find' string in length
then no. more space is required so character are simply replaced
Case 2: If replacement string is less than 'find' string in length
then some is created after replacing the characters
so another loop is required for removing that holes
Case 3: If replacement string is greater than 'find' string in length
then more space is required to be created between characters for
replacement string, after that replacement is done.
*/
//Note: This program can be modified by using list and stack
// to make it more efficient, robust and flexible.
#include<stdio.h>
#include<conio.h>
#include<string.h>
char* replace(char[],char[],char[]);
void main ()
{
char str[50]="Look Hook Nook";
clrscr();
printf("Before: %s",str);
printf("\nAfter: %s", replace(str,"k","am"));
printf("\nBefore: %s",str);
printf("\nAfter: %s", replace(str,"Loo","S"));
printf("\nBefore: %s",str);
printf("\nAfter: %s", replace(str,"Hoo","Dre"));
printf("\nBefore: %s",str);
printf("\nAfter: %s", replace(str,"ooam","ame"));
getch();
}
// This function can work with max. of 100 occurence of 'to find' string
// due to static declaration of memory limit.
char* replace(char str[],char find[],char rep[]){
int occ[100],i,j,loc,c=0,next,start;
int lens,lenf,lenr;
int diff,noOfBytes;
lens=strlen(str);
lenf=strlen(find);
lenr=strlen(rep);
//find the no. of occurence of 'find' string
for(i=0;i<lens;i++) {
loc=i;
for(j=0;j<lenf;j++){
if(str[i+j]!=find[j]){
loc=-1;
break;
}
}
if(loc!=-1){
occ[c]=loc;
c++;
}
}
//check difference between length of 'find' and 'replace' strings
diff=lenr-lenf;
//Case 1: When length of both strings is equal
if(diff==0){
for(i=0;i<c;i++){
for(j=0;j<lenr;j++){
str[occ[i]+j]=rep[j];
}
}
}
//Case 2: When length of replace string < length of find string
else if(diff<0){
//replace characters
for(i=0;i<c;i++){
for(j=0;j<lenr;j++){
str[occ[i]+j]=rep[j];
}
}
//fill holes
for(i=0;i<c;i++){
next=lens+diff*c;
if(i<c-1) next=occ[i+1]-1;
for(j=occ[i]+lenr-i;j<=next;j++){
str[j]=str[j-diff*(i+1)];
}
}
//append null character at end of string
for(i=lens-1;i>=lens+diff*c;i--){
str[i]='\0';
}
}
//Case 3: When length of replace string > length of find string
else if(diff>0){
//make space
next=lens-1;
for(i=c-1;i>=0;i--){
for(j=next;j>=occ[i];j--){
str[j+diff*c-c+i+1]=str[j];
}
next=occ[i];
}
//replace characters
for(i=0;i<c;i++){
for(j=0;j<lenr;j++){
str[occ[i]+j+i]=rep[j];
}
}
}
return str; //return result
} //End of function
//END OF PROGRAM
