C++ Program to Delete a Word from a String

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In this article, you will learn and get code to delete (or remove) a word from a string in C++. Both word and string must be entered by user at run-time.

Here are the list of programs, you will go through:

Delete a Word from a String
Modified (Complete) Version of Above Program
Delete a Word from String using a Two-Dimensional Array

Note - The first program has a limitation, that if user enters the string as this is codescracker and the word (to delete) as is. Then is from this also gets deleted. So the new string will be th codescracker. To overcome this problem, we've modified this program.

Second program (modified program) also removes extra spaces from the new string.

Delete a Word from a String

To delete any desired word from a given string in C++ programming, you have to ask from user to enter the string and word. Then delete the entered word (along with its duplicate) from the entered string.

The question is, write a program in C++ that deletes a word from a string. Here is its answer:

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
int main()
{
    char str[200], wrd[20];
    int i, j, strLen, wrdLen, tmp, chk=0;
    cout<<"Enter the String: ";
    gets(str);
    cout<<"Enter the Word: ";
    cin>>wrd;
    strLen = strlen(str);
    wrdLen = strlen(wrd);
    for(i=0; i<strLen; i++)
    {
        tmp = i;
        for(j=0; j<wrdLen; j++)
        {
            if(str[i]==wrd[j])
                i++;
        }
        chk = i-tmp;
        if(chk==wrdLen)
        {
            i = tmp;
            for(j=i; j<(strLen-wrdLen); j++)
                str[j] = str[j+wrdLen];
            strLen = strLen-wrdLen;
            str[j]='\0';
        }
    }
    cout<<"\nNew String = "<<str;
    cout<<endl;
    return 0;
}

This program was build and run under Code::Blocks IDE. Here is its sample run:

C++ program to delete word from string sentence

Now supply any string say Hello from C++, Hello from codescracker and a word say Hello. Press ENTER key to delete Hello from the entered string as shown here in the snapshot given below:

The dry run of above program with user input as provided in above sample run, goes like:

Initial value, chk=0
When user enters the string Hello from C++, Hello from codescracker, then it gets stored to str in a way that:
- str[0]=H
- str[1]=e
- str[2]=l
- and so on
Similarly the entered word say Hello gets stored to wrd in a way that:
- wrd[0]=H
- wrd[1]=e
- and so on
The function, strlen() takes a string as its argument and returns the length of the string
So strLen holds length of string, whereas wrdLen holds length of word. That is, strLen=39 and wrdLen=5
Now program flow starts evaluating the for loop
For the first time, the initialization part gets executed, and it executes only at once
So i=0 and the condition, i<strLen or 0<39 evaluates to be true, therefore program flow goes inside the loop. From next time, the value of i gets incremented and evaluates the condition. Every time, program flow goes inside the loop, until its condition evaluates to be false
Now inside the loop, the value of i (0) gets initialized to tmp
There is another for loop from here
So 0 gets initialized to j and the condition, j<wrdLen or 0<5 evaluates to be true, therefore program flow goes inside the loop and the condition str[i]==wrd[j] or str[0]==wrd[0] or H==H evaluates to be true, therefore the value of i gets incremented. So i=1
Now the value of j gets incremented. So j=1. Then the condition, j<wrdLen or 1<5 evaluates to be true, therefore program flow again goes inside the loop and the condition, str[i]==wrd[j] or str[1]==wrd[1] or e==e evaluates to be true, therefore the value of i again gets incremented
This process continues until the condition of this for loop evaluates to be false
Because, the word gets matched with the first word of the string, that is Hello, with character-by-character matching
So the value of i will be 5 after exiting from this loop, and i-tmp or 5-0 or 5 gets initialized to chk. Here 0 (tmp's value) is the previous value of i. That is, the value before entering into the inner for loop
This statements, checks whether each and every character of the word gets matched with each and every character of the string (starts from the index, before this loop)
Now because, the value of chk is equal to the value of wrdLen. So just shift all the character comes after the matched word (in string) to the 5 index back. Because 5 is the length of word
So the new string will be from C++, Hello from codescracker after executing this if's block of code
Don't forgot to initialize a null terminated character after the last character's index
Now program flow again goes back to outer for loop, increments the value of i and evaluates the condition
This process continues until the condition evaluates to be false
After exiting from the loop, just print the value of str

Note - If you want to create the same program, without using string function, strlen(), then you can refer to Count Occurrence of a Word in a String. I know the program is not same, but that article is little similar to this one. There we've counted the desired word from string without using any string function. So you can refer that article as an idea, to implement with yourself. That will be more helpful for you.

Modified Version of Previous Program

Here is the complete version of previous program that deletes a word from a string. This program also removes extra spaces from the new string.

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
int main()
{
    char str[200], wrd[20];
    int i, j, strLen, wrdLen, tmp, chk=0;
    int doIncrement, isSpace;
    cout<<"Enter the String: ";
    gets(str);
    cout<<"Enter the Word: ";
    cin>>wrd;
    strLen = strlen(str);
    wrdLen = strlen(wrd);
    for(i=0; i<strLen; i++)
    {
        tmp = i;
        doIncrement = 0;
        for(j=0; j<wrdLen; j++)
        {
            if(str[i]==wrd[j])
            {
                if(tmp>0 && (tmp+wrdLen)<strLen)
                {
                    if(str[tmp-1]== ' ' && str[tmp+wrdLen]==' ')
                        doIncrement=1;
                }
                else if(tmp==0 && (tmp+wrdLen)<strLen)
                {
                    if(str[tmp+wrdLen]==' ')
                        doIncrement=1;
                }
                else if(tmp>0 && (tmp+wrdLen)==strLen)
                {
                    if(str[tmp-1]== ' ')
                        doIncrement=1;
                }
                if(doIncrement==1)
                    i++;
                else
                    break;
            }
        }
        chk = i-tmp;
        if(chk==wrdLen)
        {
            i = tmp;
            for(j=i; j<(strLen-wrdLen); j++)
                str[j] = str[j+wrdLen];
            strLen = strLen-wrdLen;
            i = tmp;
            str[j]='\0';
        }
    }
    strLen = strlen(str);
    i=0;
    while(str[i]!='\0')
    {
        isSpace = 0;
        if(str[i]==' ' && str[i+1]==' ')
        {
            for(j=i; j<(strLen-1); j++)
            {
                str[j] = str[j+1];
                isSpace = 1;
            }
        }
        if(i==0 && str[i]==' ')
        {
            for(j=i; j<(strLen-1); j++)
            {
                str[j] = str[j+1];
                isSpace = 1;
            }
        }
        if(isSpace==0)
            i++;
        else
        {
            str[j]='\0';
            strLen--;
        }
    }
    cout<<"\nNew String = "<<str;
    cout<<endl;
    return 0;
}

Here is its sample run with user input, this is is is isth codescracker as string and is as the word to delete:

Using Two dimensional Array

Using two-dimensional array, the program becomes more easier to create or understand. Here is the program:

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
int main()
{
    char str[400], wrd[20], strInTwoDArray[20][20];
    int i, j=0, k=0;
    cout<<"Enter the String: ";
    gets(str);
    cout<<"Enter the Word (to be Delete): ";
    gets(wrd);
    for(i=0; str[i]!='\0'; i++)
    {
        if(str[i]==' ')
        {
            strInTwoDArray[k][j]='\0';
            k++;
            j=0;
        }
        else
        {
            strInTwoDArray[k][j]=str[i];
            j++;
        }
    }
    strInTwoDArray[k][j] = '\0';
    j=0;
    for(i=0; i<(k+1); i++)
    {
        if(!strcmp(strInTwoDArray[i], wrd))
            strInTwoDArray[i][j]='\0';
    }
    cout<<"\nThe New String is: ";
    j=0;
    for(i=0; i<(k+1); i++)
    {
        if(strInTwoDArray[i][j] == '\0')
            continue;
        else
            cout<<strInTwoDArray[i];
    }
    cout<<endl;
    return 0;
}

Here is its sample run with user input, is is is this is isth this is (as string) and is (as word):

delete word from string using two array c++

Same Program in Other Languages

C++ Online Test

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