16_print_reverse.cpp

/* 
    Take N as input, Calculate it's reverse also Print the reverse.
    Constraints:  0 <= N <= 1000000000

    Sample Input:   123456789
    Sample Output:  987654321

    Explanation:    You've to calculate the reverse in a number, not just print the reverse.
*/

#include<iostream>
using namespace std;

// function to calculate power
int fast_pow(int num, int power){
	if(num == 0)
		return 0;
	else if(power == 0)
		return 1;
	int res = 1;
	while(power--){
		res *= num;
	}
	return res;
}

int main() {
	int num;
	cin >> num;
	//Calculating the digit count
	int temp = num;
	int digit_count = 0;
	while (temp){
		digit_count++;
		temp /= 10;
	}
	//Calculating reverse
	int reverse = 0;
	temp = num;
	while(temp){
		int rem = temp%10;
		digit_count--;
		reverse += (rem * fast_pow(10,(digit_count)));
		temp /= 10;
	}
	cout << reverse;
	return 0;
}

/* 
    For the Given input: 123456789
    The corresponding ans is 987654321,To achieve this answer we must know how to access the last digit of a number viz, if we perform modulus 10 with any number we got the last digit of that number.

    for e.g, 123 % 10 = 3, and now to modify the number we need to remove the 3 from the digit as it is accounted so we have perfrom divide by 10 action to reduce the length by 1.
    for e.g., 123 / 10 = 12. we must perform both the operations till we got Zero as the number, and most importantly to build the ans we can construct it by multipying it by 10 and then add to the answer.
    for e.g., ans = 12, if u want to add 3 so u need to multiply 12 by 10 and then add the num, so it become 12*10 + 3 = 123.

    Code:       public static int reverse(int n){    
                    int ans = 0;        
                        while(n != 0){        
                        int digit = n % 10;
                        ans = ans *10 + digit;          
                        n /= 10;        
                        }                
                    return ans;    
                }
*/