学步园

求对称子字符串的最大长度，如abcbae，那么最大长度为5。

动态规划，O(n*n)

bool a[100][100] = {false};

int get_longest(char *b)
{
	int len = 0;
	int slen = strlen(b);

	int first = 0;
	int last = 0;

	for (last = 0; last < slen; ++last)
	{
		for (first = 0; first <= last; ++first)
		{
			if (first+1 <= last-1)
				a[last][first] = (a[last-1][first+1] && b[first]==b[last]);
			else
				a[last][first] = (b[first]==b[last]);

			if (a[last][first] && (last - first +1 > len))
				len = last - first +1 ;
		}
	}

	return len;
}