# C/C++ Program to remove alternate digits of an integer

Write a program to remove alternate digits of an integer in c/c++.

```Intput
1234567

Output
1357```

The simplest way to remove alternate digits of an integer is to convert the integer to a string using itoa() and then read the alternate digits using a loop and combine the digits together.

Steps

1. Let n be the input integer.
2. Covert n to a string using itoa(). Let the string be str.
3. Set temp = 0 and i = 0.
4. Repeat the following step while i < str.Length
1. temp = temp * 10 + str[i]
2. i = i + 2
5. The final answer is stored in temp.

## Program to remove alternate digits

```#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int removeAlternateDigits(int n)
{
char str[32];
int temp, i;

// convert integer n into a character string
// the string is placed in str
// 10 indicates n base 10
itoa(n, str, 10);

temp = 0;
// reading only alternate digits of the string
for (i = 0; i < strlen(str); i = i + 2)
{
// append str[i] to right side of temp
// str[i]-'0' converts str[i] to corresponding integer
temp = temp * 10 + (str[i] - '0');
}

return temp;

}

int main()
{
int n;
printf("Enter a Number: ");
scanf("%d", &n);

n = removeAlternateDigits(n);

printf("Number after removing alternate digits: %d", n);

}```

Output

```Enter a Number: 123456789
Number after removing alternate digits: 13579```

## Program Remove alternate digits without using string

In this section, we will discuss how we can remove alternate digits from an integer without converting integer to string.

Steps

1. Let n be the input integer.
2. Reverse n.
3. Set temp = 0.
4. Repeat the following steps while n > 0
1. temp = temp*10 + n%10
2. n = n / 100
5. The final answer is stored in temp.
```#include<stdio.h>
#include<stdlib.h>
#include<string.h>

// function to reverse n
int reverse(int n)
{
int temp = 0;
while (n > 0)
{
temp = temp * 10 + n % 10;
n = n / 10;
}
return temp;
}

int removeAlternateDigits(int n)
{
int temp = 0;
n = reverse(n);
while (n > 0) {
temp = temp * 10 + n % 10; // append n%10 to right side of temp
n = n / 100; // removing 2 digits from right side of n
}
return temp;
}

int main()
{
int n;
printf("Enter a Number: ");
scanf("%d", &n);

n = removeAlternateDigits(n);

printf("Number after removing alternate digits: %d", n);

}```

Output

```Enter a Number: 987654321
Number after removing alternate digits: 97531```