Description Farmer John had just acquired several new farms! He wants to connect the farms with roads so that he can travel from any farm to any other farm via a sequence of roads; roads already connect some of the farms. Each of the N (1 ≤ N ≤ 1,000) farms (conveniently numbered 1..N) is represented by a position (Xi, Yi) on the plane (0 ≤ Xi ≤ 1,000,000; 0 ≤ Yi ≤ 1,000,000). Given the preexisting M roads (1 ≤ M ≤ 1,000) as pairs of connected farms, help Farmer John determine the smallest length of additional roads he must build to connect all his farms. Input * Line 1: Two space-separated integers: N and M * Lines 2..N+1: Two space-separated integers: Xi and Yi * Lines N+2..N+M+2: Two space-separated integers: i and j, indicating that there is already a road connecting the farm i and farm j. Output * Line 1: Smallest length of additional roads required to connect all farms, printed without rounding to two decimal places. Be sure to calculate distances as 64-bit floating point numbers. Sample Input 4 1 1 1 3 1 2 3 4 3 1 4 Sample Output 4.00
这题与常规最小生成树一样。 然而是玄学题。。。 第一次交mle+wa，去网上找了一份交了，ac。 我不服。 改了在交re。 出了变量名都一样啊。 多交了几次，就迷之ac了。 玄不救非，珍爱生命，远离p站。
