Given a number N, write a C program to find the count of digits in the number N.
Examples:
Input: N = 12345 Output: 5 Explanation: The count of digit in 12345 = 5 Input: N = 23451452 Output: 8 Explanation: The count of digits in 23451452 = 8
Methods to Count Digits of a Number
There are a few methods to count the digits of a number mentioned below:
- Using Loops
- Logarithmic Approach
- Using Recursion
- Using Repeated Multiplication
- By Dividing with Powers of Two
1. Using Loops
The count of digits in a number can be found efficiently in a few steps:
- Remove the last digit of the number by dividing it by 10.
- Increment the count of digits by 1.
- Keep repeating steps 1 and 2 until the value of N becomes 0. In this case, there will be no more digits left in the number to count.
Example:
C
// C Program to Find Count of// Digits in a Number// Using Loops#include <stdio.h>// Find the count of digitsint findCount(int n){ int count = 0; // Remove last digit from number // till number is 0 while (n != 0) { // Increment count count++; n /= 10; } // return the count of digit return count;}// Driver programint main(){ int n = 98562; printf("Count of digits in %d = %d\n", n, findCount(n)); return 0;} |
Output
Count of digits in 98562 = 5
The complexity of the above method
Time complexity: O(D), where D is the count of digits in the number N.
Auxiliary Space: O(1)
2. Logarithmic Approach
Below is the C program to count the number of digits in a number without using a loop:
C
// C Program to Count the Number// Of Digits in a Number// Using Logarithmic Approach#include <math.h>#include <stdio.h>// Driver codeint main(){ int n = 98562; int count = 0; count = (n == 0) ? 1 : log10(n) + 1; printf("Count of digits in %d = %d\n", n, count); return 0;} |
Output
Count of digits in 98562 = 5
3. Using Recursion
Below is the C program to count the number of digits using functions:
C
// C Program to Count the Number// Of digits in a number// Using Recursion#include <stdio.h>int Count_Of_Digits(int n){ static int Count = 0; if (n > 0) { Count = Count + 1; Count_Of_Digits(n / 10); } return Count;}// Driver codeint main(){ int n = 98562, Count = 0; Count = Count_Of_Digits(n); printf("Count of digits in %d = %d\n", n, Count); return 0;} |
Output
Count of digits in 98562 = 5
4. Using Repeated Multiplication
Below is the C program to count the number of digits in a number using repeated multiplication:
C
// C Program to Count the Number// Of Digits in a Number// Using Repeated Multiplication#include <stdio.h>// function to find the count // the numberint findCount(unsigned int n){ unsigned int count = 0; unsigned int temp = 1; while (temp <= n) { count++; temp *= 10; } return count;}// Driver codeint main(){ unsigned int n = 98523, digits; // call function to count digit digits = findCount(n); printf("Count of digits in %d = %d\n", n, digits); return 0;} |
Output
Count of digits in 98523 = 5
5. By Dividing with Powers of Two
Below is the C program to count the number of digits in a number by dividing with powers of two:
C
// C Program to Count the Number// Of Digits in a Number// By Dividing with Powers of Two#include <stdio.h>int findCount(unsigned int n){ int count = 1; if (n >= 100000000) { count += 8; n /= 100000000; } if (n >= 10000) { count += 4; n /= 10000; } if (n >= 100) { count += 2; n /= 100; } if (n >= 10) { count += 1; } return count;}// Driver codeint main(){ unsigned int n = 98532, digits; // call function to count digit digits = findCount(n); printf("Count of digits in %d = %d\n", n, digits); return 0;} |
Output
Count of digits in 98532 = 5
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