类似Apple Tree
方程：
dp[a][0]=sum{dp[i][0]
            +(2*dist{i,a}|i is in M or dp[i][0]!=0)}(i is a child of a)
dp[a][1]=dp[a][0]
        -max{dp[i][0]-dp[i][1]
            +(dist{i,a}|i is in M or dp[i][0]!=0)}(i is a child of a)

• 大水题。只要找出所有经过的边，总和乘上2，然后减去一条到某个点距离最大的值，就是答案 (251) yygy 2012-11-10 00:19:16