如何在不使用數組的情況下按升序對數字進行排序？

Question

我正在努力編寫一個 C 程序，該程序按升序對從多個文件中讀取的數字進行排序。

要求：

1. 創建 3 個文件（文件 1、文件 2、文件 3）
2. 從用戶和file1中獲取數字
3. 找到最小的數字（在 file1 中）並將其復制到 file3
4. 將文件 1 中的數字復制到文件 2，但我們復制到文件 3 的最小數字除外。
5. 將 file2 中的數字復制到 file1（刪除所有舊數字）。
6. 使用 while function 重復上述步驟，直到我們在 file3 中按升序對所有數字進行排序。
7. 將數字從 file3 復制到 file1 並打印屏幕上的所有數字（來自 file1）。

注意：該程序必須僅使用文件來對數字進行排序，並且不應使用任何數組。

我為此工作了幾個小時，但現在有時它可以工作，有時它不能。 我真的不知道出了什么問題。

有關解決此問題的任何想法或建議？

#include <conio.h>
#include <stdio.h>
// to save the position of the smallest number
int pos;

// to get numbers from the user and save them in file1
void getNumbers(FILE *file) {
  char x[255];
  printf("Enter numbers: ");
  scanf("%[^\n]s", &x);
  fprintf(file, "%s", x);
}

// to find the smallest number and copy it to file3
void findSmallestNo(FILE *file1, FILE *file3) {
  int x, temp;
  rewind(file1);
  fscanf(file1, "%d", &temp);
  pos = ftell(file1);
  while (!(feof(file1))) {
    fscanf(file1, "%d", &x);
    if (x < temp) {
      temp = x;
      pos = ftell(file1);
    }
  }
  fprintf(file3, "%d ", temp);
}

// to copy numbers from file1 to file2 except the smallest number that we copied
// in the file3

void copyToFile2(FILE *file1, FILE *file2) {
  int cur_pos, x;
  rewind(file1);
  rewind(file2);
  while (!(feof(file1))) {
    fscanf(file1, "%d", &x);
    cur_pos = ftell(file1);
    if (cur_pos != pos) {
      fprintf(file2, "%d ", x);
    }
  }
}

// to copy from file2 to file1 (it should delete the old data in file1)
void copyToFile1(FILE *file1, FILE *file2) {
  int x, count = 0;
  rewind(file2);

  while (!feof(file2)) {
    count++;
    fscanf(file2, "%d", &x);
    fprintf(file1, "%d ", x);
  }
}

// to print numbers on the screen
void print_file(FILE *file1) {
  int x;
  rewind(file1);
  printf("\nSorted Numbers: ");

  while ((fscanf(file1, "%d", &x)) == 1) {
    printf("%d ", x);
  }
  printf("\n");
}

int main() {
  int len, count = 1;
  FILE *pFile1, *pFile2, *pFile3;
  pFile1 = fopen("file1.txt", "w+");
  pFile2 = fopen("file2.txt", "w+");
  pFile3 = fopen("file3.txt", "a+");
  if (pFile1 == NULL) {
    printf("Couldn't open the file\n");
    exit(1);
  }
  // to get the count of numbers in file1
  getNumbers(pFile1);
  int getLength(FILE * file) {
    int nn, counting = 1;
    rewind(file);
    while ((fscanf(file, "%d ", &nn) == 1)) {
      counting++;
    }
    return counting;
  }
  len = getLength(pFile1);

  // while loop until var count is equal to the count of numbers in file1
  while (count < len) {
    ++count;
    findSmallestNo(pFile1, pFile3);
    copyToFile2(pFile1, pFile2);
    fclose(pFile1);
    pFile1 = fopen("file1.txt", "w+");
    copyToFile1(pFile1, pFile2);
  }

  fclose(pFile1);
  fclose(pFile3);
  pFile1 = fopen("file1.txt", "w+");
  pFile3 = fopen("file3.txt", "r");

  int number;
  // to copy numbers from file3 to file1
  while (count != 1) {
    fscanf(pFile3, "%d ", &number);
    fprintf(pFile1, "%d ", number);
    --count;
  }
  // to print numbers on the screen in file1
  print_file(pFile1);
  fclose(pFile1);
  fclose(pFile2);
  fclose(pFile3);

  return 0;
}

Answer 1

//#include <conio.h>
#include <stdio.h>
// to save the position of the smallest number

// to get numbers from the user and save them in file1
void getNumbers(char *filename) {
    char x[255];
    FILE *file;
    file = fopen(filename, "w");
    if (file == NULL) {
        printf("Couldn't open the file\n");
        return;
    }
    printf("Enter numbers: ");
    scanf("%[^\n]s", &x);
    fprintf(file, "%s", x);
    fclose(file);
}

// to find the smallest number and copy it to file3
int findSmallestNo(char *filename1, char *filename3) {
    int x, temp = 100000;
    FILE *file1, *file3;
    file1 = fopen(filename1, "r");
    file3 = fopen(filename3, "a");
    fscanf(file1, "%d", &temp);
    while (fscanf(file1, "%d", &x) == 1) {
        if (x < temp) {
            temp = x;
        }
    }
    fprintf(file3, "%d ", temp);
    fclose(file1);
    fclose(file3);
    return temp;
}

// to copy numbers from file1 to file2 except the smallest number that we copied
// in the file3

void copyToFile2(char *filename1, char *filename2, int min_value) {
    int flag = 0, x;
    FILE *file1, *file2;
    file1 = fopen(filename1, "r");
    file2 = fopen(filename2, "w");
    while (fscanf(file1, "%d", &x) == 1) {
        if (x != min_value || flag == 1) {
            fprintf(file2, "%d ", x);
        } else {
            flag = 1;
        }
    }
    fclose(file1);
    fclose(file2);
}

// to copy from file2 to file1 (it should delete the old data in file1)
void copyToFile(char *filename1, char *filename2) {
    int x;
    FILE *file1, *file2;
    file1 = fopen(filename1, "w");
    file2 = fopen(filename2, "r");
    rewind(file2);

    while (fscanf(file2, "%d", &x) == 1) {
        fprintf(file1, "%d ", x);
    }
    fclose(file1);
    fclose(file2);
}

// to print numbers on the screen
void print_file(char *filename) {
    int x;
    FILE *file;
    file = fopen(filename, "r");
    printf("\nSorted Numbers: ");

    while ((fscanf(file, "%d", &x)) == 1) {
        printf("%d ", x);
    }
    printf("\n");
    fclose(file);
}

int getLength(char *filename) {
    int nn, counting = 1;
    FILE *file;
    file = fopen(filename, "r");
    rewind(file);
    while ((fscanf(file, "%d ", &nn) == 1)) {
        counting++;
    }
    fclose(file);
    return counting;
}

void clearFile (char *filename) {
    FILE *file;
    file = fopen(filename, "w");
    fclose(file);
}

int main() {
    int len, count = 1;
    char *filename1 = "file1.txt";
    char *filename2 = "file2.txt";
    char *filename3 = "file3.txt";

    clearFile(filename3);

    // to get the count of numbers in file1
    getNumbers(filename1);

    len = getLength(filename1);

    // while loop until var count is equal to the count of numbers in file1
    while (count < len) {
        ++count;
        int cur_min = findSmallestNo(filename1, filename3);
        copyToFile2(filename1, filename2, cur_min);
        copyToFile(filename1, filename2);
    }

    int number;
    // to copy numbers from file3 to file1
    copyToFile(filename1, filename3);
    clearFile(filename3);
    // to print numbers on the screen in file1
    print_file(filename1);
    return 0;
}

我修復了你的代碼，它似乎工作正常。

您的算法有效，但我認為就像@Bananenkönig 所說的“在文件之間復制效率很低。”。 您的代碼的問題只是處理文件。

您使用 fscanf 讀取文件末尾的方式將多讀 1 次才能找到 eof，這就是為什么您會在結果中得到一些不需要的數字的原因。