Reversing array logic in C not working properly

Question

I am trying to read the input to my program (a string of chars) and invert the order of the words that are in it.

For example, if I were to pass my program ABC DEF GHI JKL it would output JKL GHI DEF ABC. I am using the whitespace as separators.

My code:

char toReverse[1000];
char outputArray[1000];
int charCount = //Size of the toReverse array. Varies on the input
                //It is the total number of chars stored in the array
...
int i;
int tempCharCount = charCount;
int wordSize = 0;
int outputIndex = 0;
int sentenceIndex = 0;
int charStep = 0;
for(i = charCount-1; i>=0; i--){
    if(toReverse[i] == ' '){
        int j;
        sentenceIndex = tempCharCount - wordSize;
        for(j = 0; j<charStep; j++){
            outputArray[outputIndex++] = toReverse[sentenceIndex++];
        }
        outputArray[outputIndex] = ' ';
        outputIndex++;
        charStep = 0;
    }
    wordSize++;
    charStep++;

}

There is a flaw in my code. I do know why this happens though. For example, if I were to pass as input ABC DEF GHI, it will only output GHI DEF. This is because whenever the outer for loop reaches index 0 of my toReverse array, since it is not a space ' ', it does not do the if(toReverse[i]) inner for(j = 0; j<charStep; j++) since the condition is not met.

Do you have any advice regarding to the logic? I have tried reversing my logic, such as if(toReverse[i] != ' ') but it brings more problems than it solves.

Thanks for your advice and comments!

Cheers

Edit 1

---

I am reading my input from a file By the way!

Update 1

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Here I am basically trying to open various files and read chars from them

int main(int argc, char * argv[])
{
    int i = 1;
    FILE * fp = NULL;

    if(1==argc){
    do_read(stdin);
    }else{
    // cycle through all files in command line arguments and read them
        for (i=1; i < argc; i++) {
            if ((fp = fopen(argv[i], "r")) == NULL) {
                printf("Failed to open file.\n");
            }
            else {
                do_read(fp);
                fclose(fp);

            }
        }
    }

    //printf("\n");

    //printf("\n");
    printf("%i",charCount);
    return 0;
}

Answer 1

sample

#include <stdio.h>
#include <string.h>

void proc_rev(char toReverse[], char outputArray[]){
    int charCount = strlen(toReverse);
    int i;
    int tempCharCount = charCount;
    int wordSize = 0;
    int outputIndex = 0;
    int sentenceIndex = 0;
    int charStep = 0;
    for(i = charCount-1; i>=0; i--){
        if(toReverse[i] == ' '){
            int j;
            sentenceIndex = tempCharCount - wordSize;
            for(j = 0; j<charStep; j++){
                outputArray[outputIndex++] = toReverse[sentenceIndex++];
            }
            outputArray[outputIndex] = ' ';
            outputIndex++;
            charStep = 0;
        }
        wordSize++;
        charStep++;
    }
    outputArray[outputIndex] = '\0';
}

int main(void){
    FILE *fp = stdin;

    char toReverse[1000] = " ";
    char outputArray[1000];

    while(1 == fscanf(fp, "%998[^\n]%*c", &toReverse[1])){
        proc_rev(toReverse, outputArray);
        puts(outputArray);
    }

    return 0;
}

---

void do_read(FILE *fp){
    char toReverse[1000] = " ";
    char outputArray[1000];

    while(1 == fscanf(fp, "%998[^\n]%*c", &toReverse[1])){
        proc_rev(toReverse, outputArray);
        puts(outputArray);
    }
}

Answer 2

The current logic reverses individual words from last to second word. However to reverse the first word you will have to add a check apart from if(toReverse[i] == ' ') as the first character need not be a space. A separate check can be used when counter 'i' reaches zero, i.e. first character

Answer 3

This code is not tested but basic idea is reversing the whole string once and then reverse it word by word. idea is correct, implementation may have bugs

void swap(char* s, int i, int j) {
    char tmp = s[i];
    s[i] = s[j];
    s[j] = tmp;
}


void rev(char* stirng, int start, int len) {
    for (int i=0; i<len/2; ++i) {
       swap(string, i, len-i-1);
    }
}

int main() {
    char* string = read from file
    int len = strlen(string);
    rev(string, 0, len);

    for (int i=0; i<len;) {
        int l = 0;
        int j=i;
        while (j<len && string[j]!=' ') ++j;
        rev(string, i, j-i);
        i=j+1;
    }
}