main.c

char convert(char *s, int numRows) {
    int lenght = strlen(s);
    
    char result = (char*)malloc(lenght * sizeof(char));
    int resI = 0;
    
    int line = 0;
    int delimiter = 2;
    int advancer = 0;
    while(line < numRows){
        
        int inChar = line;
        while(inChar < lenght){
            result[resI] = s[inChar];
            resI++;
            inChar += ((s * 2) - delimiter);
            inChar += (((line + 1) * 2) - delimiter);
        }
        delimiter += 2;
        line++;
    }
    return result;
}