题目链接:点击打开链接 Description On an N × N chessboard with a non-negative number in each grid, Kaka starts his matrix travels with SUM = 0. For each travel, Kaka moves one rook from the left-upper grid
题目链接:点我啊╭(╯^╰)╮ 题目大意: 一棵无根树,定义 L ( a , b ) L(a,b) L(a,b) 为树上从 a a a 到 b b b 的路径点数 计算 p a i r s ( l 1 , l 2 ) pairs (l_1, l_2) pairs(l1,l2) , L ( a , b ) = l 1 , L ( c , d ) = l 2 L(a,