附加随机文本，不重复文件(C) [英] Append Random Text without Repetition for File (C)

问题描述

我有5个姓名列表

char *name[] = {"a","b","c","d","e"};

我有3个文件

char path1[PATH_MAX+1]
snprintf(path1, PATH_MAX+1, "%sfile1.txt",dirname);
FILES *filename1 = fopen(path1, "w")
.
.
.
char path3[PATH_MAX+1]
snprintf(path3, PATH_MAX+1, "%sfile3.txt",dirname);
FILES *filename3 = fopen(path3, "w")

我想要的是将 a，b，c，d，e (每个文件一个)随机添加到其中三个文件中，而无需重复.

What I want is to randomly append a,b,c,d,e (one of them per file) into three of those files without repetition.

我现在拥有的是(其中一个例子)

srand(time(NULL));
int one = rand()%5;
char path1[PATH_MAX+1];
snprintf(path1, PATH_MAX+1, "%sfile1.txt",dirname);
FILES *filename1 = fopen(path1, "w");
fputs(name[one],filename1);
fclose(filename1);

但是，有时我的 file1.txt 和 file3.txt 都包含 b (与名称)

However, sometimes it is still possible where my file1.txt and file3.txt both contain b (same alphabet from name)

问题

我是否错过了某些东西来确保所有随机结果总是唯一的?

Did I miss something to make sure that all the random result always unique?

用6行代码创建一个文件并在其中添加一个随机名称是否也很有效?我只是想知道是否必须创建20个文件，所以我会写120行，这些行基本相同，只是数量不同(文件名 1 到文件名 3 )

Is it also efficient tho to have 6 lines of code to create one file and append a random name inside it? I'm just wondering if I have to create like 20 files, I will write 120 lines that basically almost the same, just different in number (filename1 to filename3)

谢谢.

推荐答案

要获得唯一的字符序列，可以从逐渐减小的池中绘制它们.例如，选择a后，将从池中将其删除.当然，该池必须至少与要打印的文件数量一样大.

To get a unique sequence of characters, you can draw them from a diminishing pool. For example, after you have picked the a, it is removed from the pool. Of course, the pool must be at least as big as the number of files you want to print.

实现这种选择的一种简单方法是从池中选择一个字符，将池中的最后一个字符移动到所选择字符的位置，并将池大小减小一个.

A simple way to implement this sort of picking is to pick a char from the pool, move the last character from the pool to the place of the picked character and decrease the pool size by one.

如果您看到大量的代码重复，尤其是如果唯一的区别是沿着filename1，filename2，filename3等行的变量名称，则应该按钟声，您应该使用数组:FILE *file[NFILE].但是请注意，一次只能打开一定数量的文件.

If you see a lot of repetition of code, especially if the only difference is a variable name along the lines of filename1, filename2, filename3 and so on should ring a bell that you should use an array: FILE *file[NFILE]. Be aware, though, that you can only have a certain number of files open at a time.

在您的情况下，您想将一个字符写入文件.无需同时打开多个文件:打开文件，选择一个字符，将其写入文件，然后关闭文件.然后处理下一个文件.

In your case, you want to write a single character to a file. There's no need to have multiple file s open simultaneously: Open a file, pick a char, write it to the file, close e file. Then process the next file.

我想下面的程序可以满足您的需求.

The program below does what you want, I think.

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

#define NFILES 10

int main()
{
    char pool[] = "abcdefghij";     // Available chars as array
    int npool = sizeof(pool) - 1;   // Pool size minus terminating '\0'
    int i;

    if (npool < NFILES) {
        fprintf(stderr,
            "Not enough letters in pool for %d files.\n", NFILES);
        exit(1);
    }

    srand(time(NULL));

    for (i = 0; i < NFILES; i++) {
        int ipick = rand() % npool;    // position of pick
        char pick = pool[ipick];       // picked char

        char fname[20];
        FILE *f;

        pool[ipick] = pool[--npool];   // remove pick from pool

        snprintf(fname, sizeof(fname), "file-%03d.txt", i);

        f = fopen(fname, "w");
        if (f == NULL) {
            fprintf(stderr, "Could not create %s.\n", fname);
            exit(1);
        }

        fprintf(f, "%c\n", pick);
        fclose(f);
    }

    return 0;
}

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