qsort / bsearch

╰半橙微兮° 2023-10-09 10:32 37阅读 0赞

#### qsort bsearch ####

# include <stdlib.h> #

void qsort (void* base, size_t num, size_t size,
                int (*compar)(const void*,const void*));
    
    //第一个参数 数组
    //第二个参数 数组大小
    //第三个参数 元素大小
    //第四个参数 函数

//mark.txt
    Tom 97 68 45
    Jerry 100 32 88
    Harry 78 88 78
    Lucy 87 90 89
    Mickey 88 77 66
    Peter 59 68 98
    Alice 62 73 89

/* !< output */
    
    //按语文成绩排序
    Jerry   100     32      88
    Tom     97      68      45
    Mickey  88      77      66
    Lucy    87      90      89
    Harry   78      88      78
    Alice   62      73      89
    Peter   59      68      98
    
    Process returned 0 (0x0)   execution time : 0.006 s
    Press any key to continue.

/* qsort example */
    #include <stdio.h>      /* printf */
    #include <stdlib.h>     /* qsort */
    
    int values[] = { 40, 10, 100, 90, 20, 25 };
    
    int compare (const void * a, const void * b)
    {
      return ( *(int*)a - *(int*)b );
    }
    
    int main ()
    {
      int n;
      qsort (values, 6, sizeof(int), compare);
      for (n=0; n<6; n++)
         printf ("%d ",values[n]);
      return 0;
    }

### bsearch ###

void* bsearch (const void* key, const void* base,
                   size_t num, size_t size,
                   int (*compar)(const void*,const void*));

#include <stdlib.h>
    #include <stdio.h>
    
    typedef struct {
        char name[30];
        int Chinese;
        int Math;
        int English;
    } Student;
    
    Student students[7];
    
    void readData() {
        FILE* file = fopen("mark.txt", "r");
        int i;
        for (i = 0; i < 7; i++) {
            fscanf(file, "%s", students[i].name);
            fscanf(file, "%d", &students[i].Chinese);
            fscanf(file, "%d", &students[i].Math);
            fscanf(file, "%d", &students[i].English);
        }
        fclose(file);
    }
    
    void displayData() {
        int i;
        for (i = 0; i < 7; i++) {
            printf("%s\t", students[i].name);
            printf("%d\t", students[i].Chinese);
            printf("%d\t", students[i].Math);
            printf("%d\t", students[i].English);
            printf("%d\n", students[i].Chinese + students[i].Math + students[i].English);
        }
    }
    int compare(const void* a, const void* b) {
        Student* pa = (Student *)a;
        Student* pb = (Student *)b;
        int num1 = pa->Chinese + pa->Math + pa->English;
        int num2 = pb->Chinese + pb->Math + pb->English;
        return num2 - num1;
    }
    
    int compare2(const void* key, const void* e) {
        int* pNum1 = (int *)key;
        Student* pS = (Student *)e;
        int num1 = *pNum1;
        int num2 = pS->Math + pS->Chinese + pS->English;
        return num2 - num1;
    }
    
    int main(void) {
    
        readData();
        qsort(students, 7, sizeof(Student), compare);
        int key = 224;
        Student* s = bsearch(&key, students, 7, sizeof(Student), compare2);
        printf("%s\n", s->name);
        displayData();
        return 0;
    }
    /* output */
    /* !< 寻找总分为224的人 */
    Alice
    Lucy    87      90      89      266
    Harry   78      88      78      244
    Mickey  88      77      66      231
    Peter   59      68      98      225
    Alice   62      73      89      224
    Jerry   100     32      88      220
    Tom     97      68      45      210
    
    Process returned 0 (0x0)   execution time : 0.005 s
    Press any key to continue.

/* bsearch example */
    #include <stdio.h>      /* printf */
    #include <stdlib.h>     /* qsort, bsearch, NULL */
    
    int compareints (const void * a, const void * b)
    {
      return ( *(int*)a - *(int*)b );
    }
    
    int values[] = { 50, 20, 60, 40, 10, 30 };
    
    int main ()
    {
      int * pItem;
      int key = 40;
      qsort (values, 6, sizeof (int), compareints);
      pItem = (int*) bsearch (&key, values, 6, sizeof (int), compareints);
      if (pItem!=NULL)
        printf ("%d is in the array.\n",*pItem);
      else
        printf ("%d is not in the array.\n",key);
      return 0;
    }

/* bsearch example with strings */
    #include <stdio.h>      /* printf */
    #include <stdlib.h>     /* qsort, bsearch, NULL */
    #include <string.h>     /* strcmp */
    
    char strvalues[][20] = {"some","example","strings","here"};
    
    int main ()
    {
      char * pItem;
      char key[20] = "example";
    
      /* sort elements in array: */
      qsort (strvalues, 4, 20, (int(*)(const void*,const void*)) strcmp);
    
      /* search for the key: */
      pItem = (char*) bsearch (key, strvalues, 4, 20, (int(*)(const void*,const void*)) strcmp);
    
      if (pItem!=NULL)
        printf ("%s is in the array.\n",pItem);
      else
        printf ("%s is not in the array.\n",key);
      return 0;
    }

**reference**

[http://www.cplusplus.com/info/][http_www.cplusplus.com_info]

转载于:https://www.cnblogs.com/xuzhaoping/p/11494266.html

[http_www.cplusplus.com_info]: http://www.cplusplus.com/info/