2020-08-31

剑指offer

面试题3-|| 不修改数组查找数组中的重复数字

int getDuplication(const int* numbers, int length)
{
	if (numbers == nullptr || length < 0) return false;
	for (int i = 0; i < length; i++) {
		if (numbers[i] < 1 || numbers[i] > length - 1) return false;
	}
	int start = 1, end = length - 1;
	int middle;
	while (start <= end) {
		middle = ((end - start) >> 1) + start;
		count = countRange(numbers, length, start, middle);
		if (start == end)
		{
			if (count > 1)
				return start;
			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;
}