reversing a character string

This is a discussion on reversing a character string within the C++ Programming forums, part of the General Programming Boards category; Ah now you've provided code so its ok for us to give you some Code: for (index=0; string1[index] != '

  1. #16
    & the hat of GPL slaying Thantos's Avatar
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    Ah now you've provided code so its ok for us to give you some
    Code:
    for (index=0; string1[index] != '\0'; index++)
      ; // Empty body.  We are just trying to get index to be at the null character
    
    for (--index; // index was pointing at the null, we need to go to the previous character
        index >= 0; // when index == 0 we are at the first character
        index--) // step back to the previous character
      cout << string1[index] << endl;

  2. #17
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    So close....

    I haven't done it as a function yet, I usually try t get it working w/o using a function and then do the function...but I don't know why my output is doing funky things. I got it to output the word backwards...but it also does a bunch of weird characters. Another problem is if I type in a 5 letter word like 'angel' and then a 3 letter word like 'fie' it comes out eifna it is not clearing the memory after each run through. I thought the endl; cleared the buffer ? The last problem is in trying to break the WHILE loop. I have tried setting it to != '1' and it yells at me, I tried != 'x' and it errored...so for now I have left it at !='\0' but theres no way to escape the program. I am sorry for being such a bother. I can't even sleep because I have code swimming through my brain and until I get this fixed it is relentless....is that sad or what?


    Output 2



    Code:
    //Heather Conn
    //Program 7
    //This program will read in a word of 1-10 letters and output the word reversed
    
    #include <iostream>
    #include <iomanip>
    #include <fstream>
    
    //Declare std
    using std::cout;
    using std::cin;
    using std::endl;
    using std::ios;
    using std::cerr;
    using std::ofstream;
    
    
    //Start the program
    int main ()
    {
    
    //Declare the variables
    	char string1[10];
    	int index;
    	int idx;
    	char reverse[10];
    	
    
    //Open the file for output
    	ofstream data_out ("output.txt", ios::out);
    
    //Error routine if file can not be created
    	if (!data_out) {
    		cerr << "File could not be opened" << endl;
    		exit (1);
    	}
    
    //Describe program to user
    	cout << "This progam will output any word consisting of 1-10 characters in reverse." << endl;
    	data_out << "This progam will output any word consisting of 1-10 characters in reverse." << endl;
    
    //WHILE loop to loop program--This is not working but I am having trouble finding a value to end the loop
    	while (string1 != "\0"){
    
    //Get word and output to file
    		cout << "\nPlease enter a word 1-10 characters in length: ";
    		cin >> string1;
    		data_out << "\nThe word is: " << string1 << endl;
    
    //Initialize idx
    		idx=0;
    	
    //Set up loop
    			for (index=0; string1[index] != '\0'; index++);	//starts at 0 and counts up till it finds '\0'
    		
    			for (--index; index >= 0; index--) {
    				reverse[idx] = string1[index];
    				++idx;
    				
    			}
    			
    //Output reversed text
    				cout << "The word reversed is: " << reverse << endl;
    				data_out << "\nThe word reversed is: " << reverse << endl;
    
    //End WHILE
    	}
    
    //End program
    		return 0;
    }
    Last edited by HConn; 11-15-2004 at 04:08 AM. Reason: to add link to my output

  3. #18
    ATH0 quzah's Avatar
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    The wierd characters are because you didn't add a null to the end of the string. Remember a string by definition is a series of characters terminated with a null.

    Quzah.
    Hope is the first step on the road to disappointment.

  4. #19
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    In order for the strings to have 10 possible visible char and still have the null terminating char, each of these need to be 11 elements long, not 10.

    char string1[10];
    char reverse[10];

    When you get done reading the char of string1 into reverse, you need to give it a null char to make reverse a string, not just a char array.
    Code:
    for (--index; index >= 0; index--) 
    {
      reverse[idx] = string1[index];
    				  ++idx;
    }
    //reverse[idx] is now the first available "empty" index in reverse.
    reverse[idx] = '\0';

  5. #20
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    *lightbulb* I forgot that since there was no carriage return associated with reverse that it wouldn't automatically have a null at the end.

    Yall thanks for the help...strings/arrays are making a little more sense now. I don't know why this particular concept is so difficult for me, but at least now I can say I don't fall into the "as clear as mud" category.

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