用C写一个算术编码解码

算术编码是一种无损数据压缩算法，可以将任意长度的数据压缩成一个小数。解码时，根据压缩时使用的概率分布，将小数还原成原始数据。以下是用C语言实现算术编码解码的代码：

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

#define MAX_LEN 1000

typedef struct {
    int low;
    int high;
    int range;
} Range;

void encode(char* input, char* output) {
    int freq[256] = {0};
    int len = strlen(input);
    for (int i = 0; i < len; i++) {
        freq[input[i]]++;
    }
    int total = 0;
    for (int i = 0; i < 256; i++) {
        total += freq[i];
    }
    for (int i = 0; i < 256; i++) {
        freq[i] = (freq[i] * 10000) / total;
    }
    Range r = {0, 9999, 10000};
    int low = 0;
    int high = 9999;
    for (int i = 0; i < len; i++) {
        int c = input[i];
        int new_low = low + (r.range * freq[c]) / 10000;
        int new_high = low + (r.range * freq[c+1]) / 10000 - 1;
        r.low = new_low;
        r.high = new_high;
        while (1) {
            if (r.low / 1000 == r.high / 1000) {
                int digit = r.low / 1000;
                output[i] = digit;
                low -= digit * r.range / 10000;
                high -= digit * r.range / 10000;
                r.low = (r.low % 1000) * 10;
                r.high = (r.high % 1000) * 10 + 9;
            } else if (r.low / 10000 == 0 && r.high / 10000 == 9) {
                break;
            } else {
                r.low = (r.low % 1000) * 10;
                r.high = (r.high % 1000) * 10 + 9;
                output[i] = 0;
            }
        }
    }
    output[len] = '\0';
}

void decode(char* input, char* output) {
    int freq[256] = {0};
    int len = strlen(input);
    for (int i = 0; i < len; i++) {
        freq[input[i]]++;
    }
    int total = 0;
    for (int i = 0; i < 256; i++) {
        total += freq[i];
    }
    for (int i = 0; i < 256; i++) {
        freq[i] = (freq[i] * 10000) / total;
    }
    Range r = {0, 9999, 10000};
    int low = 0;
    int high = 9999;
    for (int i = 0; i < len; i++) {
        int c = input[i];
        int new_low = low + (r.range * freq[c]) / 10000;
        int new_high = low + (r.range * freq[c+1]) / 10000 - 1;
        r.low = new_low;
        r.high = new_high;
        int value = 0;
        for (int j = 0; j < 4; j++) {
            value = value * 10 + (r.low / (r.range / 10));
            r.low = (r.low % (r.range / 10)) * 10;
            r.high = (r.high % (r.range / 10)) * 10 + 9;
        }
        output[i] = value;
        low += freq[value] * r.range / 10000;
        high = low + freq[value+1] * r.range / 10000 - 1;
    }
    output[len] = '\0';
}

int main() {
    char input[MAX_LEN];
    char output[MAX_LEN];
    printf("请输入要压缩的字符串：");
    scanf("%s", input);
    encode(input, output);
    printf("压缩后的字符串为：");
    for (int i = 0; i < strlen(input); i++) {
        printf("%d", output[i]);
    }
    printf("\n");
    decode(output, input);
    printf("解压后的字符串为：%s\n", input);
    return 0;
}

第二个问题：lua closure factory 完整代码

以下是一个简单的Lua闭包工厂函数，可以用于创建一组具有相同行为的闭包：

function make_counter()
    local count = 0
    return function()
        count = count + 1
        return count
    end
end

local c1 = make_counter()
print(c1()) -- 输出 1
print(c1()) -- 输出 2

local c2 = make_counter()
print(c2()) -- 输出 1
print(c1()) -- 输出 3

第三个问题：中文加密

中文加密可以使用简单的替换密码，将每个中文字符替换成另一个中文字符。以下是一个简单的中文加密程序，可以将输入的中文字符串加密成另一个中文字符串：

import random

def encrypt(text):
    chars = list(text)
    random.shuffle(chars)
    return ''.join(chars)

text = input('请输入要加密的中文字符串：')
encrypted = encrypt(text)
print('加密后的字符串为：', encrypted)

解密时，只需要将加密后的字符串还原成原始字符串即可。