#include <iostream>
#include <algorithm>
#include <iterator>

using namespace std;

int arrayA[10] = {1, 3, 5, 7, 9};
int arrayB[] = {2, 4, 6, 8, 10};
const int sizeB = sizeof arrayB / sizeof *arrayB;
const int sizeA = sizeof arrayA / sizeof *arrayA - sizeB;

int* mergeArray(int *arrayA, int sizeA, int *arrayB, int sizeB)
{
 if (arrayA == NULL || arrayB == NULL || sizeA < 0 || sizeB < 0)
 return NULL;

 int posA = sizeA - 1;
 int posB = sizeB - 1;

 while (posA >= 0 && posB >= 0)
 {
 if (arrayA[posA] < arrayB[posB])
 {
  arrayA[posA + posB + 1] = arrayB[posB];
  posB--;
 }
 else
 {
  arrayA[posA + posB + 1] = arrayA[posA];
  posA--;
 }
 copy(arrayA, arrayA + 10, ostream_iterator<int>(cout, " "));
 system("pause");
 }

 return arrayA;
}

void main()
{
 int *result = mergeArray(arrayA, sizeA, arrayB, sizeB);

 copy(result, result + 10, ostream_iterator<int>(cout, " "));
 cout << endl;
}

代碼寫完后似乎完成了所需功能，但還不止于此，必須對上述代碼做UT

1. 健壯性

arrayA或arrayB為空，長度小于0

2. 邊界用例

arrayA為空，長度為1；arrayB不為空，長度大于1
首元素用例
const int size = 6;
int arrayA[size] = {2};
int arrayB[] = {0, 1, 1, 1, 1};
反之
const int size = 6;
int arrayA[size] = {0, 1, 1, 1, 1};
int arrayB[] = {2};

3. 正常用例：

const int size = 10;
int arrayA[size] = {1, 3, 5, 7, 9};
int arrayB[] = {2, 4, 6, 8, 10};

const int size = 10;
int arrayA[size] = {2, 4, 6, 8, 10};
int arrayB[] = {1, 3, 5, 7, 9};

const int size = 10;
int arrayA[size] = {1, 2, 3, 4, 5};
int arrayB[] = {6, 7, 8, 9, 10};

const int size = 10;
int arrayA[size] = {6, 7, 8, 9, 10};
int arrayB[] = {1, 2, 3, 4, 5};

經過上面的測試，不難發(fā)現(xiàn)在邊界條件用例中，代碼已經不能正確運行出結果，在測試用例的驅動下，不難寫出正確代碼如下：

int* mergeArray(int *arrayA, int sizeA, int *arrayB, int sizeB)
{
 if (arrayA == NULL || arrayB == NULL || sizeA < 0 || sizeB < 0)
 return NULL;

 int posA = sizeA - 1;
 int posB = sizeB - 1;

 while (posA >= 0 && posB >= 0)
 {
 if (arrayA[posA] < arrayB[posB])
 {
  arrayA[posA + posB + 1] = arrayB[posB];
  posB--;
 }
 else
 {
  arrayA[posA + posB + 1] = arrayA[posA];
  posA--;
 }
 copy(arrayA, arrayA + size, ostream_iterator<int>(cout, " "));
 system("pause");
 }

 //出現(xiàn)兩種情形：
 //1. posA < 0 && posB >= 0
 //2. posA >= 0 && posB < 0
 //只有第1種情形需要進行處理
 if (posA < 0 && posB >= 0)
 {
 while (posB >= 0)
 {
  arrayA[posA + posB + 1] = arrayB[posB];
  posB--;
 }
 } 
 return arrayA;
}

相信本文所述對大家C程序算法設計的學習有一定的借鑒價值。

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