Submission #19582627

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Source Code Expand

class pp_UnionFind():
    def __init__(self,N):
        from bisect import bisect
        self.INF = 1e18
        *self.p, = range(N)
        self.sz = [1]*N
        self.H = [1]*N
        self.S = [[(0, 1)] for i in range(N)]
        self.T = [self.INF]*N
    def find(self,x,t):
        while self.T[x] <= t:
            x = self.p[x]
        return x
    def union(self,x,y,t):
        px = self.find(x, t)
        py = self.find(y, t)
        if px == py:
            return 0
        if self.H[py] < self.H[px]:
            self.p[py] = px
            self.T[py] = t
            self.sz[px] += self.sz[py]
            self.S[px].append((t, self.sz[px]))
        else:
            self.p[px] = py
            self.T[px] = t
            self.sz[py] += self.sz[px]
            self.S[py].append((t, self.sz[py]))
            self.H[py] = max(self.H[py], self.H[px]+1)
        return 1
    def size(self,x, t):
        y = self.find(x, t)
        idx = bisect(self,self.S[y], (t, self.INF))-1
        return self.S[y][idx]
n,m=map(int,input().split())
uf=pp_UnionFind(n)
for i in range(m):
    a,b=map(int,input().split())
    uf.union(a-1,b-1,i)
for i in range(int(input())):
    a,b=map(int,input().split())
    a-=1
    b-=1
    ok=m
    ng=-1
    while abs(ok-ng)>1:
        num=(ok+ng)//2
        if uf.find(a,num)==uf.find(b,num):
            ok=num
        else:
            ng=num
    if ok==m:
        print(-1)
    else:
        print(ok+1)

Submission Info

Judge Result