難度：3.5/5
很多syntax要記，附在下方。1
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| #include "account.h"
#include <stdio.h>
#include <stdlib.h>
#define AGE 1
#define ZIPCODE 2
Account accts[100005];
int cmp(const void* a, const void* b){
Account *acct_a = (Account*)a;
Account *acct_b = (Account*)b;
if((acct_a->accountNum) > (acct_b->accountNum)) return 1;
else if((acct_a->accountNum) < (acct_b->accountNum)) return -1;
else return 0;
}
int cmp_age(const void* a, const void* b){
Account *acct_a = (Account*)a;
Account *acct_b = (Account*)b;
if((acct_a->age) > (acct_b->age)) return 1;
else if((acct_a->age) < (acct_b->age)) return -1;
else return 0;
}
int cmp_zipcode(const void* a, const void* b){
Account *acct_a = (Account*)a;
Account *acct_b = (Account*)b;
if((acct_a->zipcode) > (acct_b->zipcode)) return 1;
else if((acct_a->zipcode) < (acct_b->zipcode)) return -1;
else return 0;
}
int get_size(FILE *f){
int prev = ftell(f);
fseek(f, 0L, SEEK_END);
int size = ftell(f);
fseek(f, prev, SEEK_SET);
return size;
}
static inline void print_line(Account* acct){
printf("%d, %d, %d, %d\n", acct->accountNum, acct->age, acct->zipcode, acct->balance);
}
static inline void print_acct(int n){
printf("account, age, zipcode, balance\n");
for(int i = 0; i < n; i++){
print_line(&(accts[i]));
}
}
static inline void print_info(int a, int b){
printf("%d, %d\n", a, b);
}
void get_age_info(int n){
printf("age, sum_balance\n");
int now_age = accts[0].age;
int now_sum_balance = accts[0].balance;
for(int i = 1; i < n; i++){
if(accts[i].age == now_age){
now_sum_balance += accts[i].balance;
}
else{
print_info(now_age, now_sum_balance);
now_age = accts[i].age;
now_sum_balance = accts[i].balance;
}
}
print_info(now_age, now_sum_balance);
return;
}
void get_zipcode_info(int n){
printf("zipcode, sum_balance\n");
int now_zipcode = accts[0].zipcode;
int now_sum_balance = accts[0].balance;
for(int i = 1; i < n; i++){
if(accts[i].zipcode == now_zipcode){
now_sum_balance += accts[i].balance;
}
else{
print_info(now_zipcode, now_sum_balance);
now_zipcode = accts[i].zipcode;
now_sum_balance = accts[i].balance;
}
}
print_info(now_zipcode, now_sum_balance);
return;
}
int main(){
char s[256]; scanf("%s", s);
FILE *f = fopen(s, "rb");
int n = get_size(f) / sizeof(Account);
fread(accts, sizeof(Account), n, f);
qsort(accts, n, sizeof(Account), cmp);
print_acct(n);
#if defined(SORTBY) && SORTBY == AGE
qsort(accts, n, sizeof(Account), cmp_age);
get_age_info(n);
#elif defined(SORTBY) && SORTBY == ZIPCODE
qsort(accts, n, sizeof(Account), cmp_zipcode);
get_zipcode_info(n);
#endif
return 0;
}
|
編譯參數帶入Macro
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| -D{macro_name}={macro_value}
|
Ex.1
| gcc -o out -DSORTBY=ZIPCODE main.c
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找到檔案大小
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| int get_size(FILE *f){
int prev = ftell(f);
fseek(f, 0L, SEEK_END);
int size = ftell(f);
fseek(f, prev, SEEK_SET);
return size;
}
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讀取binary file到struct
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| fread({struct_arr}, sizeof({the_struct}), {n}, {file_ptr});
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用編譯時帶入的Macro
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| #if defined({macro_name}) && {macro_name} == {value_a}
#elif defined({macro_name}) && {macro_name} == {value_b}
#endif
|