arr索引和值互换

#include<stdio.h>
#include<stdlib.h>
int* index(int* arr, int len)
{
int* p = (int*)malloc(len*sizeof(int));
int i;
for (i = 0; i < len; i++)
{
p[*arr] = i;
arr++;
}
return p;
}
int main()
{
int arr[4] = { 3,2,0,1 };
int i, numsize = 4;
int * arr1;
arr1 = index(arr, numsize);
for (int i = 0; i <numsize; i++){
printf("%d ", arr1[i]);
}
printf("\n");
return 0;
}

//数组索引交换

#include<stdio.h>

#include<stdlib.h>

int* sy(int* a, int n);

int main()

{

int a[] = { 2,0,3,1 };

//sy(a, 3);

int* c;

c = sy( a,sizeof(a)/sizeof(a[0]));

for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++){

printf("%d ", c[i]);

}

printf("\n");

return 0;

}

int* sy(int* a, int n)

{

int* b = (int*)malloc(n*sizeof(int));

for (int i = 0; i < n; i++){

b[a[i]] = i;

//printf("%d ", a[i]);

}

return b;

}