C中判断字符串中是否包含另一个字符串

int charContainsToChar(char* source, char* target)//source是主串，target是子串
	{
		int i, j;
		int s_len = strlen(source);
		int t_len = strlen(target);
		if (t_len>s_len)
		{
			return -1;
		}
		for (i = 0; i <= s_len - t_len; i++)
		{
			j = 0;
			int flag = 1;
			if (source[i] == target[j])
			{
				int k, p = i;
				for (k = 0; k<t_len; k++)
				{
					if (source[p] == target[j])
					{
						p++;
						j++;
						continue;

					}
					else
					{
						flag = 0;
						break;
					}
				}
			}
			else
			{
				continue;
			}
			if (flag == 1)
			{
				return i;
			}
		}
		return -1;
	}