计数对具有重复条目的列表排序奇数结果

Question

我正在使用计数排序来对从文件中读取的数字进行排序。这似乎适用于没有重复条目的文件，但是一旦有重复项，就会出现大量的零。

你知道为什么会发生这种情况以及如何解决这个问题吗？

示例：

输入（不重复）：

  

1612 1894 3018 4212 6046 12894 13379 14408 14615 16394 17982 23004   27588 31393 33195 39526 54326 54566 67926 72479 90466 157832 703908

输出：

  

0：1612 1：1894 2：3018 3：4212 4：6046 5：12894 6：13379 7：14408 8：   14615 9：16394 10：17982 11：23004 12：27588 13：31393 14：33195 15：   39526 16：54326 17：54566 18：67926 19：72479 20：90466 21：157832 22：   703908

输入（带有重复项）：

  

1612 1894 3018 4212 6046 12894 13379 14408 14615 16394 17982 23004   27588 31393 33195 39526 54326 54566 60000 60000 60000 60000 703908

输出（见18 ++）：

  

0：1612 1：1894 2：3018 3：4212 4：6046 5：12894 6：13379 7：14408 8：   14615 9：16394 10：17982 11：23004 12：27588 13：31393 14：33195 15：   39526 16：54326 17：54566 18： 0 19： 0 20： 0 21：60000 22：60000

输入：

  

2 2 2 2 2 3 3 3 3 3

输出：

  

0： 119 1： 110 2： 2025792 3： 3249376 4： 56 < / strong> 5：2 6：2 7：2 8：2 9：2

用于生成此输出的代码片段：

int *numbers = (int *) calloc(rows, sizeof(int));

int i = 0;
int max = -1; //min
int min = 500000000; //max
while(fscanf(inputPtr, "%d", &numbers[i]) != EOF) {
  //printf("%d\n", numbers[i]);
  if(numbers[i]>max) max = (int) numbers[i];
  if(numbers[i]<min) min = (int) numbers[i];
  i++;
}

countingSort(numbers, rows, max, min);

void countingSort(int array[], const int end, const int max, const int min) {
  int i;
  const int range = max-min+1;
  int count[range+1],
      scratch[end];

  for(i=0; i<range+1; i++)
    count[i] = 0;

  /* Set the value of count[i] to the number of
   * elements in array with value i+min-1. */
  for(i=0; i<end; i++) {
    int c = array[i]-1-min;
    count[c]++;
  }

  /* Update count[i] to be the number of
   * elements with value less than i+min. */
  for(i=1; i<range; i++)
    count[i] += count[i-1];

  /* Copy the elements of array into scratch in
   * stable sorted order. */
  for(i=(end-1); i>=0; i--) {
    int c = array[i]-min;
    int s = count[c];
    scratch[s] = array[i];
    /* Increment count so that the next element
     * with the same value as the current element
     * is placed into its own position in scratch. */
    count[c]++;
  }

  for(i=0; i<end; i++)
    array[i] = scratch[i];
}

---

完整代码：

#include <stdio.h>  // FILE stderr fopen fclose fprintf printf fgets
#include <stdlib.h> // Standard Lib :-)
#include <math.h> // Every body was kung fu math

/**
 * Given any number of program parameters (command-line parameters)
 * calculates the length of each one, and writes the longest to standard output
 * this time using counting sort!
 */

/*
 * Output the usage
 */ 
void usage () {
  printf("Usage:\n"
         "Usage: part2 rows fileToRead\n");
}

/**
 * counting sort
 * http://en.wikibooks.org/wiki/Algorithm_Implementation/Sorting/Counting_sort
 */
void countingSort(int array[], const int end, const int max, const int min) {
  int i;
  const int range = max-min+1;
  int count[range+1],
      scratch[end];

  for(i=0; i<range+1; i++)
    count[i] = 0;

  /* Set the value of count[i] to the number of
   * elements in array with value i+min-1. */
  for(i=0; i<end; i++) {
    int c = array[i]-1-min;
    count[c]++;
  }

  /* Update count[i] to be the number of
   * elements with value less than i+min. */
  for(i=1; i<range; i++)
    count[i] += count[i-1];

  /* Copy the elements of array into scratch in
   * stable sorted order. */
  for(i=(end-1); i>=0; i--) {
    int c = array[i]-min;
    int s = count[c];
    scratch[s] = array[i];
    /* Increment count so that the next element
     * with the same value as the current element
     * is placed into its own position in scratch. */
    count[c]++;
  }

  for(i=0; i<end; i++)
    array[i] = scratch[i];
}

/**
 * return the appropriate percentile
 */
int getPercentile(double percent, int *array, int array_size) {
  int number = (floor(percent*array_size)+1); //-1 for arrays

  //Make number suitable for arrays
  number -= 1;

  //printf("%d\n", number);

  //Ensure the numbers aren't the same
  while(array[number-1]==array[number]) {
    number++;

    if(number>=array_size)
      return -1;
  }

  //printf("%d\n", number);

  return (int) array[number];
}

/**
 * The main method
 * part2 1000 datafile
 */ 
int main (int argc, char *argv[]) {
  //I need three args
  //1 rows
  //2 file name
  if(argc==3) {
    int rows = 0;     
    if(sscanf(argv[1], "%d", &rows) == 0) {
      printf("The number of rows must be a number.\n");
      usage();   
      exit(-1);       
    }

    FILE *inputPtr; //File pointers
    inputPtr = fopen(argv[2], "r"); //same as PHP ;-)

    // Sensible errors
    if(inputPtr==NULL) {
      printf("I could not open the file for input.\n");
      usage();
      exit(-1);
    }

    // Read all the numbers
    int *numbers = (int *) calloc(rows, sizeof(int));

    int i = 0;
    int max = -1; //min
    int min = 500000000; //max
    while(fscanf(inputPtr, "%d", &numbers[i]) != EOF) {
      //printf("%d\n", numbers[i]);
      if(numbers[i]>max) max = (int) numbers[i];
      if(numbers[i]<min) min = (int) numbers[i];
      i++;
    }

    printf("%d, %d, %d\n\n", min, max, rows);

    //int array[], const int end, const int max, const int min) {
    countingSort(numbers, rows, max, min);

    for(i = 0; i < rows; i++) {
      printf("%i: %d\n", i, numbers[i]);
    }  
    printf("-------\n\n");

    // Close the files
    //fclose(inputPtr);
    //not pointing to file anymore

    int percentile = getPercentile(0.9, numbers, rows);

    printf("%s: %d\n", argv[2], percentile);

  } else {
    printf("Please provide two CLI's!\n");
    usage();
    return 0;
  }


  /* All done */
  return 0;

}

Answer 1

这是一个错误：

/* Set the value of count[i] to the number of
 * elements in array with value i+min-1. */
for(i=0; i<end; i++) {
    int c = array[i]-1-min;
    count[c]++;
}

如果评论正确，您应该设置c = array[i]+1-min;。没有别人跳出来。