一个指针参数的例子

 

一个指针参数的例子

 

要在函数内给指针分配空间，则必须传递指针的地址，而不是指针存放的数据地址，因为我们要改变的是指针的
内容。其实原则就是要改变谁的内容就的将他的地址给别人。new操作其实作了两个操作，分配空间和改变指针的

内容。

#include <iostream>

#include <string>

 

using namespace std;

void separateOddsAndEvens(const int arr[], int size, int **odds, int * numOdds, int** evens, int* numEvens)

{

     int i;

     *numOdds = *numEvens = 0;

     for(i =0; i< size; i++)

     {

         if(arr[i]%2==1)

              (*numOdds)++;

         else

              (*numEvens)++;

     }

     *odds = new int[*numOdds];

     *evens = new int[*numEvens];

     int oddsPos = 0, evensPos = 0;

     for(i = 0; i< size; i++)

     {

         if(arr[i]% 2 == 1)

              (*odds)[oddsPos++] = arr[i];

         else

              (*evens)[evensPos++] = arr[i];

     }

}

 

void separateOddsAndEvens2(const int arr[], int size, int *odds, int * numOdds, int* evens, int* numEvens)

{

     int i;

     *numOdds = *numEvens = 0;

     for(i =0; i< size; i++)

     {

         if(arr[i]%2==1)

              (*numOdds)++;

         else

              (*numEvens)++;

     }

     odds = new int[*numOdds];

     evens = new int[*numEvens];

     int oddsPos = 0, evensPos = 0;

     for(i = 0; i< size; i++)

     {

         if(arr[i]% 2 == 1)

              odds[oddsPos++] = arr[i];

         else

              evens[evensPos++] = arr[i];

     }

}

 

int main(void)

{

     int unSplit[10] = {1,2,3,4,5,6,7,8,9,10};

     int *oddNums, *evenNums;

     int numOdds, numEvens;

 

     separateOddsAndEvens(unSplit, 10, &oddNums, &numOdds, &evenNums, &numEvens);

     separateOddsAndEvens2(unSplit, 10, &oddNums, &numOdds, &evenNums, &numEvens);  //错误,

     for(int i=0; i < numEvens ; i++)

         cout<< evenNums[i] << ",";

 

     cout << endl;

     for(int i=0; i < numOdds ; i++)

         cout<< oddNums[i] << ",";

     return 1;

}