Reverse words in string

This is a discussion on Reverse words in string within the C Programming forums, part of the General Programming Boards category; Hi, I have written a program to reverse words in a string. So if the input is: "My name is ...

  1. #1
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    Join Date
    Oct 2010
    Posts
    11

    Reverse words in string

    Hi, I have written a program to reverse words in a string. So if the input is: "My name is Jack", the output should be "yM eman si kcaJ".

    But my program is not outputting anything.

    Code:
    #include <stdio.h>
    #include <string.h>
    int main(){
    	char str[100];
    	char temp[100];
    	int i, j, k; 
    	int start = 0;
    	printf("Enter string:");
    	gets(str);
    	for (i = 0; i < strlen(str); i++){
    		if (str[i] == " "){
    			k = 0;
    			for (j = start; j < i; j++){
    				temp[k] = str[j];
    				k++;
    			}
    			temp[k] = '\0';
    			strrev(temp);
    			printf("%s", temp);
    			start = i + 1;
    		}
    	}
    	return 0;
     }
    Anyone know why my program is not outputting anything?

  2. #2
    Registered User
    Join Date
    Sep 2008
    Posts
    200
    Well, one thing is that this line will never (or rather, is very unlikely to) evaluate to true:

    Code:
    if (str[i] == " ")
    since you're comparing a char to a string. Change it to:

    Code:
    if (str[i] == ' ')
    and take it from there.

  3. #3
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    Oct 2010
    Posts
    11

    Thanks!

    Thanks JohnGraham! That solves a big part of the problem.

    But it is still not printing the reverse of the last word of the string. For example, when the input is "Hello how are you", the program outputs "olleH woh era". The last word is not reversed. Here's the code (which I have modified) again:

    Code:
    #include <stdio.h>
    #include <string.h>
    int main(){
    	char str[100];
    	char temp[100];
    	int i, j, k; 
    	int start = 0;
    	printf("Enter string:");
    	gets(str);
    	for (i = 0; i < strlen(str); i++){
    		if (str[i] == ' ' || str[i] == '\0'){ /* modified this statement */
    			k = 0;
    			for (j = start; j < i; j++){
    				temp[k] = str[j];
    				k++;
    			}
    			temp[k] = '\0';
    			strrev(temp);
    			printf("%s ", temp);
    			start = i + 1;
    		}
    	}
    	return 0;
    }
    Anyone know why it is not reversing the last word?

  4. #4
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    Join Date
    Oct 2010
    Posts
    11

    Solved

    Wait, my question is solved. The program now reverses the last word too. Here's the modified final code:

    Code:
    #include <stdio.h>
    #include <string.h>
    int main(){
    	char str[100];
    	char temp[100];
    	int i, j, k; 
    	int start = 0;
    	printf("Enter string:");
    	gets(str);
    	for (i = 0; i <= strlen(str); i++){
    		if (str[i] == ' ' || str[i] == '\0'){
    			k = 0;
    			for (j = start; j < i; j++){
    				temp[k] = str[j];
    				k++;
    			}
    			temp[k] = '\0';
    			strrev(temp);
    			printf("%s ", temp);
    			start = i + 1;
    		}
    	}
    	return 0;
    }

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