In 7-bit ZOJ - 3713(进制操作转换)

7位编码字符串长度

最新推荐文章于 2021-05-17 10:22:07 发布

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本文介绍了一种使用7位编码来存储字符串长度的方法，适用于短字符串，并提供了编码过程的详细说明及示例输入输出。

In 7-bit

ZOJ - 3713

Very often, especially in programming contests, we treat a sequence of non-whitespace characters as a string. But sometimes, a string may contain whitespace characters or even be empty. We can have such strings quoted and escaped to handle these cases. However, a different approach is putting the length of the string before it. As most strings are short in practice, it would be a waste of space to encode the length as a 64-bit unsigned integer or add a extra separator between the length and the string. That's why a 7-bit encoded integer is introduced here.

To store the string length by 7-bit encoding, we should regard the length as a binary integer. It should be written out by seven bits at a time, starting with the seven least-significant (i.e. 7 rightmost) bits. The highest (i.e. leftmost) bit of a byte indicates whether there are more bytes to be written after this one. If the integer fits in seven bits, it takes only one byte of space. If the integer does not fit in seven bits, the highest bit is set to 1 on the first byte and written out. The integer is then shifted by seven bits and the next byte is written. This process is repeated until the entire integer has been written.

With the help of 7-bit encoded integer, we can store each string as a length-prefixed string by concatenating its 7-bit encoded length and its raw content (i.e. the original string).

Input

There are multiple test cases. The first line of input is an integer T indicating the number of test cases.

Each test case is simply a string in a single line with at most 3000000 characters.

Output

For each test case, output the corresponding length-prefixed string in uppercase hexadecimal. See sample for more details.

Sample Input

3
42
yukkuri shiteitte ne!!!
https://en.wikipedia.org/wiki/Answer_to_Life,_the_Universe,_and_Everything#Answer_to_the_Ultimate_Question_of_Life.2C_the_Universe_and_Everything_.2842.29

Sample Output

023432
1779756B6B75726920736869746569747465206E65212121
9A0168747470733A2F2F656E2E77696B6970656469612E6F72672F77696B692F416E737765725F746F5F4C6966652C5F7468655F556E6976657273652C5F616E645F45766572797468696E6723416E737765725F746F5F7468655F556C74696D6174655F5175657374696F6E5F6F665F4C6966652E32435F7468655F556E6976657273655F616E645F45766572797468696E675F2E323834322E3239

code:

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
char a[3000003];
int main(){
    int t;
    cin >> t;
    getchar();
    while(t--){
        gets(a);
        int len = strlen(a);
        int l = len;
        if(!l){
            printf("00\n");
        }
        else{
            while(l){
                int tmp = l % 128;//取后七位数字
                l /= 128;//右移七位
                if(l){
                    tmp += 128;//第八位上变成1
                }
                printf("%02X",tmp);
            }
            int i;
            for(i = 0; i < len; i++){
                printf("%02X",a[i]);
            }
            puts("");
        }
    }
    return 0;
}