String Operations

Implement operations on Strings.

Source Code

#include<stdio.h>
#include<string.h>
void Insert(char*, char*, int);
void Delete(char*, int, int);
int Replace(char*, char*, char*);
int Find(char*, char*);
int main(){
  char str[50],substr[20],newstr[20];
  int index,choice,pos,len;
  printf("Enter string:\n");
  gets(str);
  printf("::STRING OPERATIONS::\n1. Insertion\n2. Deletion\n3. Find Substring\n4. Replace\n5. Exit\n");
  printf("Select string operation:\n");
  scanf("%d",&choice);
  switch(choice){
  case 1:
      printf("Enter substring to insert:\n");
      scanf("%c");
      gets(substr);
      printf("Enter position:\n");
      scanf("%d",&pos);
      if(pos<strlen(str)){
        Insert(str,substr,pos);
        printf("After insertion string is:\n%s\n",str);
      }
      else
        printf("Insertion is not possible.\n");
      break;
    case 2:
      printf("Enter position:\n");
      scanf("%d",&pos);
      printf("Enter length:\n");
      scanf("%d",&len);
      if(pos+len < strlen(str)){
        Delete(str,pos,len);
        printf("After deletion string is:\n%s\n",str);
      }else{
        printf("Cannot perform deletion operation.\n");
      }
      break;
    case 3:
      printf("Enter substring:\n");
      scanf("%c");
      gets(substr);
      index = Find(str, substr);
      if(index==-1)
        printf("'%s' is not found in '%s'.\n",substr,str);
      else
        printf("'%s' is found in '%s' at %d position.\n",substr,str,index);
      break;
    case 4:
      printf("Enter old string:\n");
      scanf("%c");
      gets(substr);
      printf("Enter new string:\n");
      gets(newstr);
      index = Replace(str,substr,newstr);
      if(index==-1)
        printf("Replace is not possible.\n");
      else
        printf("After replace string is:\n%s\n",str);
      break;
    case 5:
      exit(0);
    default:
      printf("Invalid choice.\n");
  }
  return 0;
}

void Insert(char* str, char* substr,int pos){
  int i,j;
  for(i=0;i<strlen(substr);i++){
    for(j=strlen(str)+1;j>pos;j--)
      str[j] = str[j-1];
  }
  for(i=0,j=pos;i<strlen(substr);i++,j++)
    str[j] = substr[i];
}

void Delete(char* str,int pos,int len){
  int i,j;
  for(i=1;i<=len;i++){
    for(j=pos;j<strlen(str);j++)
      str[j] = str[j+1];
  }
}

int Find(char* str, char* substr){
  int i,j,k;
  for(i=0;str[i]!='\0';i++){
    for(k=i,j=0;substr[j]!='\0';j++,k++){
      if(str[k]!=substr[j])
        break;
    }
    if(j==strlen(substr)){
      return i;
    }
  }
  if(i==strlen(str))
    return -1;
}

int Replace(char* str,char* oldstr,char* newstr){
  int oldstrpos;
  oldstrpos = Find(str,oldstr);
  if(oldstrpos==-1)
    return -1;
  else{
    Delete(str,oldstrpos,strlen(oldstr));
    Insert(str,newstr,oldstrpos);
  }
}

Enter string:
Hello how are you?
::STRING OPERATIONS::
1. Insertion
2. Deletion
3. Find Substring
4. Replace
5. Exit
Select string operation:
2
Enter position:
6
Enter length:
3
After deletion string is:
Hello  are you?