# Replacing a digit in a number with another digit in C++

In this CPP tutorial, we are going to discuss how to replace a digit in a number with any other digit.

## Integer to String Conversion

To convert an integer to a string we use t0_string() command.

Syntax:-

`to_string( num );`

Here, integer num will convert to the string.

Ex:-

```int num;

cin>>num;

string s = to_string( num );```

Now, num will convert to string and s holds its value as a string. Now, we can apply string operations on num.

## String To Integer Conversion

To convert string to an integer we use stoi() command.

Syntax:-

stoi( str );

Here, str is the string to which we need to convert to integer.

Ex:-

```string str;

cin>>str;

int num = stoi( str );```

Here, string str is converted to an integer and its value is stored in num as an integer.

## Character to an Integer Conversion

To convert character to an integer we use proper casting.

Syntax:-

int( c – ‘0’ );

where c is the character needed to be converting to an integer.

Ex:-

```char c;

cin>>c;

cout<<int(c-'0')+2<<endl;```

So, here c is converted to an integer so we can perform integer operation on it such as addition, subtraction etc. When c is character its not possible.

### Step  by Step Approach

• Input a number num.
• Input the number to which we need to replace x and from which it should be replaced y.
• Convert the number to string using to_string() function and store the string in s.
• Now, read character by character of string s and check when u get x then add y to str otherwise s[i].
• Directly we can’t compare the character to a number so we need to cast character to int.
• So, final string which we got is str having replaced digits now convert str to integer using stoi() function and store its value in res.
• Print res.

### CPP Code implementation

```#include<bits/stdc++.h>

using namespace std;

int main()
{
int num,x,y,i,res;

cin>>num;

string s,str;

cout<<"Enter the digit to be replaced"<<endl;

cin>>x;

cout<<"Enter the digit from which it should be replaced"<<endl;

cin>>y;

s=to_string(num);

for(i=0;i<s.length();i++)
{
if(int(s[i]-'0')==x)
{
str+=to_string(y);
}

else
{
str+=s[i];
}
}

res=stoi(str);

cout<<res<<endl;

}```

INPUT

```11123

Enter the digit to be replaced
1

Enter the digit from which it should be replaced
5```

OUTPUT

`55523`