一个数组，含有重复元素，给出两个数num1和num2，求这两个数字在数组中出现的位置的最小距离

O(n)时间复杂度，O(1)空间复杂度

int minDistance(int A[], int size, int num1, int num2)
{
	int num1_last_pos = -1;
	int num2_last_pos = -1;
	int min_dist = INT_MAX;
	for(int i = 0; i < size; ++i)
	{
		if(A[i] == num1)
		{
			num1_last_pos = i;
			if(num2_last_pos >= 0)
				min_dist = min(min_dist, num1_last_pos-num2_last_pos);
		}
		if(A[i] == num2)
		{
			num2_last_pos = i;
			if(num1_last_pos >= 0)
				min_dist = min(min_dist, num2_last_pos-num1_last_pos);
		}
	}
	return min_dist;
}