/*
  Name:    qsort-example2.c
  Purpose: Illustrates the use of the qsort() library function 
  Author:  Bill Slough
*/

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

#define PER_LINE 5

int compare_ints(const void *p, const void *q);
void display_ints(int x[ ], int n);
void display_strings(char *x[ ], int n);
int compare_strings(const void *p, const void *q);

int main(void) {
    int values[ ] = {120, 150, 30, 10, 130, 20, 90, 110,
                     140, 70, 80, 60, 50, 40, 100};
    int values_size = sizeof(values)/sizeof(int);

    char *elements[ ] = {"hydrogen", "lithium", "sodium", "potassium",
                         "beryllium", "magnesium", "calcium", "strontium",
                         "barium", "radium"};
    int elements_size = sizeof(elements)/sizeof(char *);

    /* Process the integer array */
    printf("Before sorting:\n");
    display_ints(values, values_size);

    /* sort them */
    qsort(values, values_size, sizeof(int), compare_ints);
    
    printf("\nAfter sorting:\n");
    display_ints(values, values_size);

    /* Process the string array */
    
    printf("\nBefore sorting:\n");
    display_strings(elements, elements_size);

    /* sort them... */
    qsort(elements, elements_size, sizeof(char *), compare_strings);
    
    printf("\nAfter sorting:\n");
    display_strings(elements, elements_size);
    
    return 0;
}

/* compare two integer values */
int compare_ints(const void *p, const void *q) {
    /* Cast the input parameters into the specific types */
    const int *p1 = (const int *) p;
    const int *q1 = (const int *) q;

    /* return negative, zero, or positive for <, ==, or > */
    if (*p1 < *q1)
        return -1;
    else if (*p1 > *q1)
        return +1;
    else
        return 0;
}

/* output the n integer values of an array x */
void display_ints(int x[ ], int n) {
    int i;

    for (i = 0; i < n; i++) {
        printf("%3d |", x[i]);
        if ((i + 1) % PER_LINE == 0)
            printf("\n");
    }
}

/* compare two string values */
int compare_strings(const void *p, const void *q) {
    /* Cast the input parameters into the specific types */
    const char **p1 = (const char **) p;
    const char **q1 = (const char **) q;

    /* return negative, zero, or positive for <, ==, or > */
    return strcmp(*p1, *q1);
}

/* output the n string values of an array x */
void display_strings(char *x[ ], int n){
    int i;

    for (i = 0; i < n; i++) {
        printf("%12s |", x[i]);
        if ((i + 1) % PER_LINE == 0)
            printf("\n");
    }  
}