字符串中查找子串，並返回子串相對字符換的位置

int FindSubstring(const char* all, const char* sub)
{
	int all_len = strlen(all);
	int sub_len = strlen(sub);
	int i = 0, j = 0;
	for (;i<all_len;++i)
	{
		if (all[i] == sub[0])
		{
			for (j=1; j<sub_len; ++j)
			{
				if (sub[j]==all[++i])
				{
					continue;
				}
				else
				{
					break;
				}
			}
			if (j == sub_len)
			{
				return (i-sub_len+1);
			}
		}
	}
	return -1;
}

int main()
{

    const char* all = "hello";
    const char* sub = "el";
    int npos = FindSubstring(all, sub);//npos = 1;
}