<OFFER03>03_01_DuplicationInArray

 #include<cstdio>

 bool duplicate(int numbers[], int length, int* duplication)
 {
     if (numbers == nullptr || length <= )
         return false;
     for (int i = ; i < length; ++i)
     {
         if (numbers[i] <  || numbers[i] > length - )
             return false;

     }
     for (int i = ; i < length; ++i)
     {
         while (numbers[i] != i)
         {
             if (numbers[i] == numbers[numbers[i]])
             {
                 *duplication = numbers[i]; //
                 return true;
             }

             int temp = numbers[i];
             numbers[i] = numbers[temp];
             numbers[temp] = temp;

         }
         return false;
     }
 }
 // test codes
 bool contains(int array[], int length, int number)
 {
     for (int i = ; i < length; ++i)
     {
         if (array[i] == number)
             return true;
     }
     return false;
 }
 void test(char* testName, int numbers[], int lengthNumbers, int expected[], \
     int expectedExpected, bool validArgument)
 {
     printf("%s begins: ", testName);
     int duplication;
     bool validInput = duplicate(numbers, lengthNumbers, &duplication);

     if (validArgument == validInput)
     {
         if (validArgument)
         {
             if (contains(expected, expectedExpected, duplication))
                 printf("Passed.\n");
             else
                 printf("Failed.\n");
         }
         else
             printf("Passed.\n");
     }
     else
         printf("Failed.\n");
 }

 void test1()
 {
     int numbers[] = { ,,,, };
     int duplications[] = {  };
     test("Test1", numbers, sizeof(numbers) / sizeof(int), duplications, sizeof(duplications) / sizeof(int), true);
 }
 void test3()
 {
     int numbers[] = { ,,,, };
     int duplications[] = { , };
     test("Test1", numbers, sizeof(numbers) / sizeof(int), duplications, sizeof(duplications) / sizeof(int), true);
 }

 // 无效的输入
 void test6()
 {
     int* numbers = nullptr;
     int duplications[] = { - }; // not in use in the test function
     test("Test6", numbers, , duplications, sizeof(duplications) / sizeof(int), false);
 }

 // 没有重复的数字
 void test4()
 {
     int numbers[] = { , , , ,  };
     int duplications[] = { - }; // not in use in the test function
     test("Test4", numbers, sizeof(numbers) / sizeof(int), duplications, sizeof(duplications) / sizeof(int), false);
 }

 // 没有重复的数字
 void test5()
 {
     int numbers[] = { , , , ,  };
     int duplications[] = { - }; // not in use in the test function
     test("Test5", numbers, sizeof(numbers) / sizeof(int), duplications, sizeof(duplications) / sizeof(int), false);
 }
 // 重复的数字是数组中最大的数字
 void test2()
 {
     int numbers[] = { , , , ,  };
     int duplications[] = {  };
     test("Test2", numbers, sizeof(numbers) / sizeof(int), duplications, sizeof(duplications) / sizeof(int), true);
 }
 void main()
 {
     test1();
     test2();
     test3();
     test4();
     test5();
     test6();
 }