用C语言写一个解决01背包问题的程序，程序会输入一个文件，要求如下：The input txt file has 3 lines. The first line has only one integer, the capacity of the bag. The second line has a bunch of positive integers for the value of each item. Two integers are separated by a comma “,”. The third line is in the same format as the second for the weight of each item. - When the calculation is finished, print the optimal value and optimal solution(s) one for each line on the screen. (The optimal value is unique, but the optimal solution may not.) - Sort the items in the optimal solution(s) in the decreasing order of item indices. - The index of items starts from 1.

以下是解决01背包问题的C语言程序，可以实现读取输入txt文件，计算最优解并输出：

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

#define MAX_ITEMS 1000

int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s input_file\n", argv[0]);
        return 1;
    }

    // 打开输入文件
    FILE *input_file = fopen(argv[1], "r");
    if (!input_file) {
        printf("Failed to open input file.\n");
        return 1;
    }

    // 读取背包容量
    int capacity;
    fscanf(input_file, "%d", &capacity);

    // 读取物品价值和重量
    int values[MAX_ITEMS], weights[MAX_ITEMS];
    int item_count = 0;
    while (!feof(input_file)) {
        int value, weight;
        fscanf(input_file, "%d,%d", &value, &weight);
        if (value <= 0 || weight <= 0) {
            break;
        }
        values[item_count] = value;
        weights[item_count] = weight;
        item_count++;
    }

    // 计算最优解
    int dp[MAX_ITEMS + 1][capacity + 1];
    for (int i = 0; i <= item_count; i++) {
        for (int j = 0; j <= capacity; j++) {
            if (i == 0 || j == 0) {
                dp[i][j] = 0;
            } else if (weights[i - 1] <= j) {
                int include = values[i - 1] + dp[i - 1][j - weights[i - 1]];
                int exclude = dp[i - 1][j];
                dp[i][j] = include > exclude ? include : exclude;
            } else {
                dp[i][j] = dp[i - 1][j];
            }
        }
    }

    // 输出最优解
    printf("%d\n", dp[item_count][capacity]);
    for (int i = item_count, j = capacity; i > 0 && j > 0; i--) {
        if (dp[i][j] != dp[i - 1][j]) {
            printf("%d ", i);
            j -= weights[i - 1];
        }
    }
    printf("\n");

    // 关闭输入文件
    fclose(input_file);

    return 0;
}

要使用该程序，需要将上述代码保存为一个C语言源文件（例如`knapsack.c`），然后使用编译器进行编译和链接，例如：

gcc -o knapsack knapsack.c

最后，运行程序时需要指定输入txt文件的路径作为参数，例如：

./knapsack input.txt

其中`input.txt`是包含背包容量、物品价值和重量的输入文件。