how to reverse order of words in string using C? - c

Question

I am trying to reverse the order of words in a string, but my output is a bunch of junk that makes no sense. I don't know what is the problem, maybe the loops are broken.
Appreciate it if someone can explain what is wrong with my code below. I still new to C programming and this kind of problem is kind of frustrating.
#include<stdio.h>
int main()
{
//declare variable
char string[100], rev_string[100];
//declare number of loop
int i, j, len;
printf("enter the string: ");
scanf("%s",string);
//finding the length
len = strlen(string);
printf("strings length: %d\n", len);
for (i = len - 1; i >= 0; i--)
for (j = 0; j < len - 1; j++)
rev_string[j] = string[i];
rev_string[j] = '\0';
if (strcmp(string, rev_string) == 0)
printf("rev_string: %s is a palindrome", rev_string);
else
printf("rev_string : %s is not a palindrome words",rev_string);
return(0);
}

Answer 1

Your title is a bit confusing because your code seems to be a palindrome check and it should reverse the string, not the order of the words.
To reverse the string you can simply do:
for (i = 0; i < len; i++)
rev_string[i] = string[len - i - 1];

Answer 2

This code can help you :
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#define NCHARS 256 /* constant to count array size, covers ASCII + extended ASCII */
int ispalindrom (const char *s1, const char *s2)
{
int count[NCHARS] = {0}; /* counting array, covers all extended ASCII */
for (; *s1; s1++) /* loop over chars in string 1 */
if (!isspace(*s1)) /* if not whitespace */
count[(int)*s1]++; /* add 1 to index corresponding to char */
for (; *s2; s2++) /* loop over chars in string 2 */
if (!isspace(*s2)) /* if not whitespace */
count[(int)*s2]--; /* subtract 1 from index corresponding to char */
for (int i = 0; i < NCHARS; i++) /* loop over counting array */
if (count[i]) /* if any index non-zero, not anagram */
return 0;
return 1; /* all chars used same number of times -> anagram */
}
void main()
{
int i, j = 0, k = 0, x, len;
char str[100], str1[10][20], temp;
char str2[100];
printf("enter the string :");
scanf("%[^\n]s", str);
for (int i = 0;str[i] != '\0'; i++)
{
str2[i]=str[i];
}
/* reads into 2d character array */
for (int i = 0;str[i] != '\0'; i++)
{
if (str[i] == ' ')
{
str1[k][j]='\0';
k++;
j=0;
}
else
{
str1[k][j]=str[i];
j++;
}
}
str1[k][j] = '\0';
/* reverses each word of a given string */
for (int i = 0;i <= k;i++)
{
len = strlen(str1[i]);
for (int j = 0, x = len - 1;j < x;j++,x--)
{
temp = str1[i][j];
str1[i][j] = str1[i][x];
str1[i][x] = temp;
}
}
for (int i = 0;i <= k;i++)
{
printf("%s ", str1[i]);
}
printf("\n\n");
if (ispalindrom(str1, str2)==0)
{
printf("The word is Palindrom !\n");
}
else
{
printf("The word is not Palindrom !\n");
}
}

Answer 3

#include <stdbool.h>
#include <stdio.h>
bool ispalindrom(char *str,int k)
{
for(int i=0;i<k;i++)
{
if(str[i]!=str[k-i-1])
{
return false;
}
}
return true;
}
int main()
{
char string[100];
printf("enter the string: ");
scanf("%s",string);
if (ispalindrom(string,strlen(string)))
{
printf("\nrev_string: %s is a palindrome\n", string);
}
else
{
printf("\nrev_string : %s is not a palindrome words\n",string);
}
}

Answer 4

you can use a loop first to reverse the string first and then use strcomp()
#include<stdio.h>
#include <string.h>
int main()
{
//declare variable
char string[100], rev_string[100];
//declare number of loop
int i, j =0 , len;
printf("enter the string: ");
scanf("%s",string);
//finding the length
len = strlen(string);
printf("strings length: %d\n", len);
for (i = len - 1;i >= 0;i--){
rev_string[j] = string[i];
j++;
}
//check the rev_string if you want
/*for (i = 0; i < len; i++){
printf("%c\n",rev_string[i]);
}*/
if(strcmp(rev_string,string) == 0){
printf("Is Palindrome\n");
return(0);
}else{
printf("Is not Palindrome\n");
return(1);
}
}