EX_rerange_chat.c

#include <stdio.h>
#include <stdlib.h>
#define MESSAGE_LENGTH 64
#define NAME_LENGTH 10

struct timestamp {
    int hour, minute;
};

struct message_info {
    struct timestamp time;
    char name[NAME_LENGTH];
    char message[MESSAGE_LENGTH];
};

int cmp(const void *a, const void *b);
void sort_message(struct message_info *m, int *total);

int main(void) {
    struct message_info m[100];
    int total;
    scanf("%d", &total);
    for(int i = 0; i < total; i++)
        scanf("%d:%d %s %[^\n]", &m[i].time.hour, &m[i].time.minute, m[i].name, m[i].message);
    sort_message(m, &total);
    for(int i = 0; i < total; i++)
        printf("%02d:%02d %s %s\n", m[i].time.hour, m[i].time.minute, m[i].name, m[i].message);
    return 0;
}
// Your code goes here

int cmp(const void* a, const void* b) {
    if(((struct message_info*)a)->time.hour>((struct message_info*)b)->time.hour){
        return 1;
    }else if(((struct message_info*)b)->time.hour>((struct message_info*)a)->time.hour){
        return -1;
    }else{
        if(((struct message_info*)a)->time.minute>((struct message_info*)b)->time.minute){
            return 1;
        }else if(((struct message_info*)b)->time.minute>((struct message_info*)a)->time.minute){
            return -1;
        }
    }
    return 0;
}

void sort_message(struct message_info *m, int *total) {
// m is array of each message information wrapped in a struct
// total is the number of total message
    qsort(m,*total,sizeof(struct message_info),cmp);
}