Insert sub-string at a position

Posted on Apr 22, 2020

C program to insert a sub-string in to given main string at a given position.

Program

#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>
#define MAX 50

void insert(char str1[MAX], char str2[MAX], int pos)
{
    int i, j, len1, len2;

    len1 = strlen(str1);
    len2 = strlen(str2);
    if(pos<=0 || pos>len1+1)
    {
        printf("\nInsertion can not be done at this position");
        getch();
        exit(0);
    }

    else
    {
        for(i=0;i<len2;i++)
        {
            for(j=len1-1+i;j>=pos-1+i;j--)
            {
                str1[j+1] = str1[j];
            }
        }

        j = pos-1;
        for(i=0;i<len2;i++)
        {
            str1[j] = str2[i];
            j++;
        }

        str1[len1+len2] = '\0';
    }
}

void main()
{
	char str1[MAX], str2[MAX];
    char ch;
    int pos;

    printf("Enter the main string\t:");
    gets(str1);
    printf("Enter the substring to be inserted\t:");
    gets(str2);
    printf("Enter the position at which it is to be inserted\t:");
    scanf("%d",&pos);

    insert(str1, str2, pos);

    printf("\nModified string\t:%s",str1);

    getch();
}

Output

Enter the main string   :welcome to course.com
Enter the substring to be inserted      :crux
Enter the position at which it is to be inserted        :18

Modified string :welcome to coursecrux.com