24/06/24(12.1117)指针进阶 ,冒泡和快排习题为依托巩固概念(strlen,sizeof,字符串,数组,指针大小的区别)

回调函数

回过头来调用的函数

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

int Find_Max(int arr[], int n){
   int max_value = arr[0];
   for (int i = 1; i < n; ++i){
       if (max_value < arr[i])
           max_value = arr[i];
   }
   return max_value;
}

int Find_Min(int arr[], int n){
   int min_value = arr[0];
   for (int i = 1; i < n; ++i){
       if (min_value > arr[i])
           min_value = arr[i];
   }
   return min_value;
}
int main(){
   int arr[] = { 5, 8, 9, 2, 3, 1, 0, 4 };
   int n = sizeof(arr) / sizeof (arr[0]);

   printf("max_value = %d\n",Find_Max(arr,n));
   printf("min_value = %d\n",Find_Min(arr, n));
   system("pause");
   return 0;
}

怎么写出一个通用的函数,可以想查找最大就是最大,想查找最小就是最小

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

int Find_Max(int arr[], int n){
   int max_value = arr[0];
   for (int i = 1; i < n; ++i){
       if (max_value < arr[i])
           max_value = arr[i];
   }
   return max_value;
}

int Find_Min(int arr[], int n){
   int min_value = arr[0];
   for (int i = 1; i < n; ++i){
       if (min_value > arr[i])
           min_value = arr[i];
   }
   return min_value;
}
//
int Find(int arr[], int n, int(*pfun)(int arr[], int n)){//通用
   return pfun(arr, n);
}

int main(){
int arr[] = { 5, 8, 9, 2, 3, 1, 0, 4 };
int n = sizeof(arr) / sizeof (arr[0]);

// printf("max_value = %d\n",Find_Max(arr,n));
// printf("min_value = %d\n",Find_Min(arr, n));
printf("max_value = %d\n",Find(arr,n,Find_Min));

system("pause");
return 0;
}

只要是有函数参数里有函数参数当参数的就是回调函数.

冒泡排序:

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

void PrintArr(int arr[], int n){
   for (int i = 0; i < n; i++){
       printf("%d",arr[i]);
   }
   printf("\n");
}
void bob(int arr[],int n){
   for (int i = 0; i < n - 1; i++){
       for (int j = 0; j < n - i - 1; j++){
           if (arr[j] > arr[j + 1]){
               int tmp = arr[j];
               arr[j] = arr[j + 1];
               arr[j + 1] = tmp;
           }

       }
   }
}
int main(){
   int arr[] = { 5, 8, 9, 2, 3, 1, 0, 4 };
   int n = sizeof(arr) / sizeof (arr[0]);
   PrintArr(arr, n);
   bob(arr, n);
   PrintArr(arr,n);
   system("pause");
   return 0;
}

改成快速排序:

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

       }
   }
}
int comp_int(const void *a, const void *b){
   const int *pa = (const int*)a;
   const int *pb = (const int*)b;
   return (*pa - *pb);
}
int main(){
   int arr[] = { 5, 8, 9, 2, 3, 1, 0, 4 };
   int n = sizeof(arr) / sizeof (arr[0]);
   PrintArr(arr, n);
   //bob(arr, n);
   qsort(arr, n, sizeof(int), comp_int);
   PrintArr(arr,n);
   system("pause");
   return 0;
}

简单的概念强化:

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

int main(){
char arr[] = { 'a', 'b', 'c', 'd', 'e', 'f', };

   printf("%d\n", sizeof(arr)); // 6
   printf("%d\n", sizeof(arr + 0)); // 4(一个地址的大小)
   printf("%d\n", sizeof(*arr)); // 1
   printf("%d\n", sizeof(arr[1])); // 1
   printf("%d\n", sizeof(&arr)); // 4
   printf("%d\n", sizeof(&arr[0] + 1)); //4
   printf("%d\n", sizeof(&arr + 1)); // 4
   printf("%d\n", strlen(arr)); // ?(随机数)
   printf("%d\n", strlen(arr + 0)); // ?
   printf("%d\n", strlen(*arr)); // 无(取的是一个字符,没法求字符串长度)
   printf("%d\n", strlen(arr[1])); // 无
   printf("%d\n", strlen(&arr)); // ?
   printf("%d\n", strlen(&arr + 1)); // ?
   printf("%d\n", strlen(&arr[0] + 1)); // ?

system("pause");
return 0;
}

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

int main(){
char arr[] ="abcdef";

   printf("%d\n", sizeof(arr)); // 7
   printf("%d\n", sizeof(arr + 0)); // 4(一个地址的大小)
   printf("%d\n", sizeof(*arr)); // 1
   printf("%d\n", sizeof(arr[1])); // 1
   printf("%d\n", sizeof(&arr)); // 4
   printf("%d\n", sizeof(&arr[0] + 1)); //4
   printf("%d\n", sizeof(&arr + 1)); // 4
   printf("%d\n", strlen(arr)); // 6
   printf("%d\n", strlen(arr + 0)); // 6
   //printf("%d\n", strlen(*arr)); // 无
   //printf("%d\n", strlen(arr[1])); // 无
   printf("%d\n", strlen(&arr)); // 6
   printf("%d\n", strlen(&arr + 1)); // ?
   printf("%d\n", strlen(&arr[0] + 1)); // 5

system("pause");
return 0;
}

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

int main(){
char *p ="abcdef";

   printf("%d\n", sizeof(p)); // 4
   printf("%d\n", sizeof(p + 0)); // 4(一个地址的大小)
   printf("%d\n", sizeof(*p)); // 1
   printf("%d\n", sizeof(p[0])); // 1
   printf("%d\n", sizeof(&p)); // 4
   printf("%d\n", sizeof(&p[0] + 1)); //4
   printf("%d\n", sizeof(&p + 1)); // 4
   printf("%d\n", strlen(p)); // 6
   printf("%d\n", strlen(p + 1)); // 5
   //printf("%d\n", strlen(*p)); // 无
   //printf("%d\n", strlen(p[0])); // 无
   printf("%d\n", strlen(&p)); // ?
   printf("%d\n", strlen(&p + 1)); // ?
   printf("%d\n", strlen(&p[0] + 1)); // 5

system("pause");
return 0;
}