找出重复的元素

1、找出重复的元素

int getDuplication(const int* numbers, int length)
{
if(numbers == nullptr || length <= 0)
return -1;
int start = 1;
int end = length - 1;
while(end >= start)
{
int middle = ((end - start) >> 1) + start;
int count = countRange(numbers, length, start, middle);
if(end == start)
{
if(count > 1)
return start;//找出了重复的数字并返回了
else
break;
}

if(count > (middle - start + 1))
end = middle;
else
start = middle + 1;
}
return -1;
}

int countRange(const int* numbers, int length, int start, int end)
{
if(numbers == nullptr)
return 0;

int count = 0;
for(int i = 0; i < length; i++)
if(numbers[i] >= start && numbers[i] <= end)
++count;
return count;
}//用来抱着数字还在这个数组里面