Problem p03682 (python)

Fixed submission:
# -*- coding: utf-8 -*-
import heapq
import sys
sys.setrecursionlimit(10**6)
N = input()
a = []
for i in range(N):
	x,y=map(int,raw_input().split())
	a.append((i,x,y))

#a => point,x,y
a1=sorted(a, key=lambda x: x[1])
a2=sorted(a, key=lambda x: x[2])


#Union Find
#初めは各頂点が根
par=[ i for i in range(N) ]
#木の根を求める
def root(x):
	if par[x]==x:
		return x
	else:
		r=root(par[x])
		#経路圧縮
		par[x]=r
		return r
#xとyが同じ集合に属するか
def same(x,y):
	return root(x)==root(y)

#xとyが同じ根に所属していた場合、連結
def unite(x,y):
	x=root(x)
	y=root(y)
	if x==y:
		return
	else:
		par[x]=y


b=[]
for i in range(N-1):
	# len_x,x,y
	heapq.heappush( b, ( abs(a1[i+1][1]-a1[i][1]),a1[i][0],a1[i+1][0],  ))

for i in range(N-1):
	# len_y,x,y
	heapq.heappush( b, ( abs(a2[i+1][2]-a2[i][2]),a2[i][0],a2[i+1][0],  ))

#print "# b"
#print b


ans=0
cnt=0
for i in range(len(b)):
	if cnt==N-1:
		break
	val=heapq.heappop(b)
	#２点が同じ根でない場合は、木を結合する
	if not same(val[1],val[2]):
		unite(val[1],val[2])
		ans+=val[0]
		cnt+=1

print ans

Buggy submission (verdict: Runtime Error):
import sys
from  heapq import heappush, heappop, heapify

N=input()

par=[ i for i in range(N) ]

def root(x):
	if par[x]==x:
		return x
	else:
		par[x]=root( par[x] )
		return par[x]

def same(x,y):
	return root(x)==root(y)

def unite(x,y):
	x=root(x)
	y=root(y)
	if x==y: return
	par[x]=y



X=[]
Y=[]
for i in range(N):
	x,y=map(int, sys.stdin.readline().split()) 
	X.append( (x,i) )
	Y.append( (y,i) )

X.sort(key=lambda x: x[0])
Y.sort(key=lambda x: x[0])

hq=[]
for i in range(N-1):
	d=abs( X[i+1][0]-X[i][0] )
	x1=X[i][1]
	x2=X[i+1][1]
	heappush( hq, (d,x1,x2) )

	d=abs( Y[i+1][0]-Y[i][0] )
	x1=Y[i][1]
	x2=Y[i+1][1]
	heappush( hq, (d,x1,x2) )


ans=0
while hq:
	d,a,b=heappop(hq)
	if not same(a,b):
		ans+=d
		unite(a,b)
		
print ans

Buggy submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
import heapq
N = input()
a = []
for i in range(N):
	x,y=map(int,raw_input().split())
	a.append((i,x,y))

#a => point,x,y
a1=sorted(a, key=lambda x: x[1])
a2=sorted(a, key=lambda x: x[2])


#Union Find
#初めは各頂点が根
par=[ i for i in range(N) ]
#木の根を求める
def root(x):
	if par[x]==x:
		return x
	else:
		r=root(par[x])
		#経路圧縮
		par[x]=r
		return r
#xとyが同じ集合に属するか
def same(x,y):
	return root(x)==root(y)

#xとyが同じ根に所属していた場合、連結
def unite(x,y):
	x=root(x)
	y=root(y)
	if x==y:
		return
	else:
		par[x]=y


b=[]
for i in range(N-1):
	# len_x,x,y
	heapq.heappush( b, ( abs(a1[i+1][1]-a1[i][1]),a1[i][0],a1[i+1][0],  ))

for i in range(N-1):
	# len_y,x,y
	heapq.heappush( b, ( abs(a2[i+1][2]-a2[i][2]),a2[i][0],a2[i+1][0],  ))

#print "# b"
#print b


ans=0
cnt=0
for i in range(len(b)):
	if cnt==N-1:
		break
	val=heapq.heappop(b)
	#２点が同じ根でない場合は、木を結合する
	if not same(val[1],val[2]):
		unite(val[1],val[2])
		ans+=val[0]
		cnt+=1

print ans

Buggy submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
import heapq
N = input()
a = []
for i in range(N):
	x,y=map(int,raw_input().split())
	a.append((i,x,y))

#a => point,x,y
a1=sorted(a, key=lambda x: x[1])
a2=sorted(a, key=lambda x: x[2])


#Union Find
#初めは各頂点が根
par=[ i for i in range(N) ]
#木の根を求める
def root(x):
	if par[x]==x:
		return x
	else:
		r=root(par[x])
		#経路圧縮
		par[x]=r
		return r
#xとyが同じ集合に属するか
def same(x,y):
	return root(x)==root(y)

#xとyが同じ根に所属していた場合、連結
def unite(x,y):
	x=root(x)
	y=root(y)
	if x==y:
		return
	else:
		par[x]=y


b=[]
for i in range(N-1):
	# len_x,x,y
	heapq.heappush( b, ( abs(a1[i+1][1]-a1[i][1]),a1[i][0],a1[i+1][0],  ))

for i in range(N-1):
	# len_y,x,y
	heapq.heappush( b, ( abs(a2[i+1][2]-a2[i][2]),a2[i][0],a2[i+1][0],  ))

#print "# b"
#print b


ans=0
for i in range(len(b)):
	val=heapq.heappop(b)
	if not same(val[1],val[2]):
		unite(val[1],val[2])
		ans+=val[0]

print ans