Program 5.8 - Another Alternate Version

[dennishenley]

I wanted to display the digits in a row. The problem I encountered was a number that ends in zero will drop the zero when reversed. So I used this code to be able to display a number with a leading zero. I'm sure there's a more elegant way using format specifiers, but I was happy to get this to work.

Code: (Objective-C)

//
//  main.m
//  Program 5.8 - reverse digits of number
//
//  Created by Dennis Henley on 9/22/11.
//  Copyright 2011. All rights reserved.
//

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[])
{

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    unsigned int origNum, reverseNum, tempNum, tempNum2;
    
    Boolean zeroFlag;   //if reverse number starts with zero set flag so the zero can be displayed
    
    //get input from keyboard
    NSLog (@"Enter a positive integer to be reversed.");
    scanf ("%u",&origNum);
    
    //initialize variables
    tempNum = origNum;  //save origNum for later display
    reverseNum = 0;
    zeroFlag = FALSE;
    
    while ( tempNum != 0) {
        reverseNum *= 10;                    //multiply reverseNum by 10 to move 1 digit to left
        tempNum2 = tempNum % 10;             //grab right digit by getting remainder
        if(tempNum2 ==0) zeroFlag = TRUE;    //if right digit is zero set flag to allow zero display
        reverseNum += tempNum2;              //add right digit to reverseNum
        tempNum /= 10;                       //remove right digit from source by dividing by 10
        }
   
    //output results
    
    if (zeroFlag)                              //if zeroFlag is true, first reversed digit is zero
        {
        NSLog(@"The reverse of %u is 0%u", origNum, reverseNum);
        }
    else                                       //no starting zero; just display number
        {
        NSLog(@"The reverse of %u is %u", origNum, reverseNum);
        }
        
    [pool drain];
    return 0;
}

Here's sample output:


2011-09-23 08:44:37.585 reverse[1231:903] Enter a positive integer to be reversed.
4560
2011-09-23 08:44:56.281 reverse[1231:903] The reverse of 4560 is 0654