嗶哩嗶哩稿件號轉換

3-27 Upd：稍微優化了一下代碼，快速冪其實根本沒有必要。原先的代碼就撤下了。
——
前幾天B站官方更改了稿件號碼的表示形式，許多人懷念過去的av號，那麼今天我提供一個C++代碼來轉換av號與BV號。
算法來自知乎大佬。
代碼中並沒有關於算法的註釋，但我想在看完算法之後理解代碼應該不會有太大問題。
我本地的文件名爲convert.cpp.
文件下載地址

#include<cstdio>
#include<cstring>
typedef long long LL;
char table[] = "fZodR9XQDSUm21yCkr6zBqiveYah8bt4xsWpHnJE7jL5VG3guMTKNPAwcF";
int tr[1005];
int pos[] = {11, 10, 3, 8, 4, 6};
#define XORNUM 177451812
#define ADDNUM 8728348608LL
#define MODE 0//0:file_call_mode, 1:input_mode
LL decode(char* BVnumber) {
	LL r = 0, Pow58 = 1;
	for(int i = 0; i < 6; ++i) {
		r += tr[(int)BVnumber[pos[i]]];
		Pow58 *= 58;
	}
	return (r - ADDNUM) ^ XORNUM;
}
char BVtemp[15] = "BV1  4 1 7  ";
char* encode(LL avnumber) {
	avnumber = (avnumber ^ XORNUM) + ADDNUM;
	static char BVnumber[15] = "BV1  4 1 7  ";
	LL Pow58 = 1;
	for(int i = 0; i < 6; ++i) {
		BVnumber[pos[i]] = table[avnumber / Pow58 % 58];
		Pow58 *= 58;
	}
	return BVnumber;
}
bool checkBV(char* BVnumber) {
	for(int i = 0; i < 12; i++)
		if(BVtemp[i] != 32 && BVtemp[i] != BVnumber[i])
			return false;
	return true;
}
#if MODE == 0
int main(int argc, char** argv) {
	if(argc == 1) {
		puts("EXAMPLE1: \"convert av170001\" (without quotes)");
		puts("EXAMPLE2: \"convert BV17x411w7KC\" (without quotes)");
		return 0;
	}
	for(int id = 1; id < argc; id++) {
#else
int main() {
#endif
		for(int i = 0; i < 58; ++i) tr[(int)table[i]] = i;
		LL avnumber;
#if MODE == 0
		char *number = argv[id];
#else
	char number[15];
	while(scanf("%s", number) != EOF) {
#endif
		if(number[0] == 'a' && number[1] == 'v') {
			sscanf(number, "av%lld", &avnumber);
			printf("%s is converted to %s\n", number, encode(avnumber));
		} else if(number[0] == 'B' && number[1] == 'V') {
			if(checkBV(number)) printf("%s is converted to av%lld\n", number, decode(number));
			else puts("Please check the BV number you entered.");
		}
	}
	return 0;
}

上述代碼中包含了兩種形式的程序。爲防止有些人（我自己）看不懂，下面拆分了一下。

文件調用型

#include<cstdio>
#include<cstring>
typedef long long LL;
char table[] = "fZodR9XQDSUm21yCkr6zBqiveYah8bt4xsWpHnJE7jL5VG3guMTKNPAwcF";
int tr[1005];
int pos[] = {11, 10, 3, 8, 4, 6};
#define XORNUM 177451812
#define ADDNUM 8728348608LL
LL decode(char* BVnumber) {
	LL r = 0, Pow58 = 1;
	for(int i = 0; i < 6; ++i) {
		r += tr[(int)BVnumber[pos[i]]];
		Pow58 *= 58;
	}
	return (r - ADDNUM) ^ XORNUM;
}
char BVtemp[15] = "BV1  4 1 7  ";
char* encode(LL avnumber) {
	avnumber = (avnumber ^ XORNUM) + ADDNUM;
	static char BVnumber[15] = "BV1  4 1 7  ";
	LL Pow58 = 1;
	for(int i = 0; i < 6; ++i) {
		BVnumber[pos[i]] = table[avnumber / Pow58 % 58];
		Pow58 *= 58;
	}
	return BVnumber;
}
bool checkBV(char* BVnumber) {
	for(int i = 0; i < 12; i++)
		if(BVtemp[i] != 32 && BVtemp[i] != BVnumber[i])
			return false;
	return true;
}
int main(int argc, char** argv) {
	if(argc == 1) {
		puts("EXAMPLE1: \"convert av170001\" (without quotes)");
		puts("EXAMPLE2: \"convert BV17x411w7KC\" (without quotes)");
		return 0;
	}
	for(int id = 1; id < argc; id++) {
		for(int i = 0; i < 58; ++i) tr[(int)table[i]] = i;
		LL avnumber;
		char *number = argv[id];
		if(number[0] == 'a' && number[1] == 'v') {
			sscanf(number, "av%lld", &avnumber);
			printf("%s is converted to %s\n", number, encode(avnumber));
		} else if(number[0] == 'B' && number[1] == 'V') {
			if(checkBV(number)) printf("%s is converted to av%lld\n", number, decode(number));
			else puts("Please check the BV number you entered.");
		}
	}
	return 0;
}

直接打開型

#include<cstdio>
#include<cstring>
typedef long long LL;
char table[] = "fZodR9XQDSUm21yCkr6zBqiveYah8bt4xsWpHnJE7jL5VG3guMTKNPAwcF";
int tr[1005];
int pos[] = {11, 10, 3, 8, 4, 6};
#define XORNUM 177451812
#define ADDNUM 8728348608LL
LL decode(char* BVnumber) {
	LL r = 0, Pow58 = 1;
	for(int i = 0; i < 6; ++i) {
		r += tr[(int)BVnumber[pos[i]]];
		Pow58 *= 58;
	}
	return (r - ADDNUM) ^ XORNUM;
}
char BVtemp[15] = "BV1  4 1 7  ";
char* encode(LL avnumber) {
	avnumber = (avnumber ^ XORNUM) + ADDNUM;
	static char BVnumber[15] = "BV1  4 1 7  ";
	LL Pow58 = 1;
	for(int i = 0; i < 6; ++i) {
		BVnumber[pos[i]] = table[avnumber / Pow58 % 58];
		Pow58 *= 58;
	}
	return BVnumber;
}
bool checkBV(char* BVnumber) {
	for(int i = 0; i < 12; i++)
		if(BVtemp[i] != 32 && BVtemp[i] != BVnumber[i])
			return false;
	return true;
}
int main() {
	for(int i = 0; i < 58; ++i) tr[(int)table[i]] = i;
	LL avnumber;
	char number[15];
	while(scanf("%s", number) != EOF) {
		if(number[0] == 'a' && number[1] == 'v') {
			sscanf(number, "av%lld", &avnumber);
			printf("%s is converted to %s\n", number, encode(avnumber));
		} else if(number[0] == 'B' && number[1] == 'V') {
			if(checkBV(number)) printf("%s is converted to av%lld\n", number, decode(number));
			else puts("Please check the BV number you entered.");
		}
	}
	return 0;
}