[PKU 2104 2761] 区间第k大（小）值
{
这一类问题方法很多
是练习数据结构的经典问题
建议可以线段树写一遍 用平衡树再写一遍
用树状数组也可以解决
平衡树也可以试试2种不同的方法
比如Splay和SBT
(虽然Splay不是平衡树 也不如平衡树效率高
但是Splay可以和平衡树互补解决问题
姑且笼统的把Splay归到平衡树里吧
况且很多区间问题还是少不了Splay树的
这里运用的还是平衡树的有序性 不是Splay特有的提根操作)
特殊的情况如区间最小值用RMQ解决很方便
总之 经典的题目就是和各种方法有千丝万缕的联系
需要慢慢体会
}
原题 http://acm.pku.edu.cn/JudgeOnline/problem?id=2104
http://acm.pku.edu.cn/JudgeOnline/problem?id=2761
题意
给定一个长为n的序列
给定q个询问{b,' ',e,' ',k}
求区间[b,e]内的第k小值
数据结构
平衡树 线段树(排序树 划分树 归并树) 树状数组
算法
线段树
//建议用于解决2104
先用线段树把归并排序的过程存下来
![[PKU 2104 2761] 区间第k大（小）值](http://img.e-com-net.com/image/product/d78cfef78cbb434d988c7491bb7e77c7.jpg)
比如序列2 9 5 8 3 7 10 4
如图归并的过程就记录在了一棵线段树里
具体操作可以在建树的时候实现
此时建树的复杂度是对每个节点进行2路归并的总复杂度
等于x+x/2*2+x/4*4......每一层其实是一样的复杂度是O(nlog2n)
然后是查询
查询可以用二分答案来实现
对于一个区间[b,e] 我们对序列内的数进行二分
设当前二分得的答案是Mid
我们仅需解决Mid在[b,e]内的排名Rank即可
调用Get函数可以解决这个问题
由于每个节点内元素有序 所以Get函数内置二分查找 用于查找给定节点内的Mid值
如果所查区间完全包含于[b,e]则直接查找
否则递归查找子结点中Mid值的排位累加就是在[b,e]内的排位了
这里需要注意一点细节
如果所查元素不在所查序列中 则排位是假设插入之后的排位
例如在{2 3 4 5 8}中9排6,7排5,2排1......
元素x在A序列排位a 在B序列排位b 则在AB归并后应排在a+b-1处 即累加要注意减1
给个例子吧 A={2 3 4} B={5 7 8} x=6
则a=4 b=2 所以6在AB归并后序列{2 3 4 5 7 8}里排第5大
Get值返回后用于确定继续二分还是返回答案
注意有时Get返回值为k时 Mid可以不在[b,e]中 需要判断
最后即可得到答案
平衡树
//建议用来解决2761 还少讨论一种情况
平衡树的思想相对好理解
将所查区间存下来 按头排序 依次查询
平衡树内保存当前查询的值
分三种情况讨论
第一种是前一个区间和当前区间不相交
则删除前一个区间内所有元素 插入当前区间所有元素
第二种是相交但不包含
则删除前一个区间除交集以外的部分 插入当前区间除交集以外的部分
第三种是区间为包含关系
则删除前一个区间出交集以外的所有部分(一前一后)
//在2761内可以不讨论最后一个情况
讨论三种情况相当于除去了很多冗余计算 也算一个强剪枝
（具体有多强需要数学帝考证 ms用柯西不等式外加微分法求函数极值可以解决－－纯属感觉）
查找符合Rank值要求的数时直接利用平衡树进行select操作即可
树状数组
//这个我只是了解一下算法 没有写
有一个大神的算法好像是这样的
不知道有没有歪解
先离散化 用1-n离散n个数
对于区间[b,e]的查询 设前一个区间为[b0,e0]
先依次删除[b0,e0]内的每个数i 即{insert(i,-1)}
再插入区间[b,e]内的每个数i即{insert(i,1)}
随后sum[x]-sum[x-1]就是第x个数的排位了
（数组里存数的个数 运用了计数排序的思想）
同样运用二分答案解决问题
需要注意输答案的时候不要把离散后的数输出去 要还原一下
//好像由于常数相当小 比前2个算法还快
我的程序
SortTree
1
const
max
=
500000
;
2
var
w,c,l,r,ls,rs,id:
array
[
1
..max]
of
longint;
3
d:
array
[
1
..
20
,
0
..max]
of
longint;
4
n,m,i,t,l0,r0,rank,s,k:longint;
5
mid:longint;
6
procedure
build(a,b,dep:longint);
7
var
x,y,l1,l2,i,j,p,q:longint;
8
begin
9
inc(t); x:
=
t;
10
l[x]:
=
a; r[x]:
=
b;
11
if
b
-
a
=
1
12
then
begin
inc(d[dep][
0
]); id[x]:
=
d[dep][
0
];
13
d[dep][id[x]]:
=
c[r[x]]; exit;
end
14
else
begin
15
y:
=
(a
+
b)shr
1
;
16
ls[x]:
=
t
+
1
; build(a,y,dep
+
1
);
17
rs[x]:
=
t
+
1
; build(y,b,dep
+
1
);
18
end
;
19
id[x]:
=
d[dep][
0
]
+
1
;
20
k:
=
d[dep][
0
]; i:
=
id[ls[x]]; j:
=
id[rs[x]]; p:
=
ls[x]; q:
=
rs[x];
21
l1:
=
r[p]
-
l[p]
+
i
-
1
; l2:
=
r[q]
-
l[q]
+
j
-
1
;
22
while
(i
<=
l1)
and
(j
<=
l2)
do
23
if
d[dep
+
1
][i]
<
d[dep
+
1
][j]
24
then
begin
inc(k); d[dep][k]:
=
d[dep
+
1
][i]; inc(i);
end
25
else
begin
inc(k); d[dep][k]:
=
d[dep
+
1
][j]; inc(j);
end
;
26
if
i
>
l1
then
while
j
<=
l2
do
27
begin
inc(k); d[dep][k]:
=
d[dep
+
1
][j]; inc(j);
end
;
28
if
j
>
l2
then
while
i
<=
l1
do
29
begin
inc(k); d[dep][k]:
=
d[dep
+
1
][i]; inc(i);
end
;
30
d[dep][
0
]:
=
k;
31
end
;
32
function
get(v,x,dep:longint):longint;
33
var
l0,r0,mid:longint;
34
begin
35
get:
=
1
;
36
if
(s
<=
l[x])
and
(r[x]
<=
t)
37
then
begin
38
l0:
=
id[x]; r0:
=
id[x]
+
r[x]
-
l[x]
-
1
;
39
while
l0
<=
r0
do
40
begin
41
mid:
=
(l0
+
r0)shr
1
;
42
if
d[dep][mid]
=
v
then
break;
43
if
d[dep][mid]
<
v
then
l0:
=
mid
+
1
;
44
if
d[dep][mid]
>
v
then
r0:
=
mid
-
1
;
45
end
;
46
if
d[dep][mid]
=
v
then
exit(mid
-
id[x]
+
1
);
47
if
d[dep][mid]
<
v
then
exit(mid
-
id[x]
+
2
);
48
if
d[dep][mid]
>
v
then
exit(mid
-
id[x]
+
1
);
49
end
50
else
begin
51
mid:
=
(l[x]
+
r[x])shr
1
;
52
if
s
<
mid
then
get:
=
get
+
get(v,ls[x],dep
+
1
)
-
1
;
53
if
t
>
mid
then
get:
=
get
+
get(v,rs[x],dep
+
1
)
-
1
;
54
end
;
55
end
;
56
begin
57
assign(input,
'
kth.in
'
);
58
reset(input);
59
assign(output,
'
kth.out
'
);
60
rewrite(output);
61
readln(n,m);
62
for
i:
=
1
to
n
do
63
read(c[i]);
64
t:
=
0
;
65
build(
0
,n,
1
);
66
for
i:
=
1
to
n
do
67
begin
68
l0:
=
1
; r0:
=
n;
69
while
l0
<=
r0
do
70
begin
71
mid:
=
(l0
+
r0)shr
1
;
72
if
d[
1
][mid]
<
c[i]
then
l0:
=
mid
+
1
;
73
if
d[
1
][mid]
=
c[i]
then
break;
74
if
d[
1
][mid]
>
c[i]
then
r0:
=
mid
-
1
;
75
end
;
76
w[mid]:
=
i;
77
end
;
78
for
i:
=
1
to
m
do
79
begin
80
readln(s,t,k);
81
s:
=
s
-
1
;
82
l0:
=
1
; r0:
=
n;
83
while
l0
<=
r0
do
84
begin
85
mid:
=
(l0
+
r0)shr
1
;
86
rank:
=
get(d[
1
][mid],
1
,
1
);
87
if
(rank
=
k)
and
(w[mid]
<=
t)
and
(w[mid]
>=
s
+
1
)
88
then
begin
writeln(d[
1
][mid]); break;
end
;
89
if
rank
<=
k
then
l0:
=
mid
+
1
else
r0:
=
mid
-
1
;
90
end
;
91
end
;
92
close(input);close(output);
93
end
.
94
SBT
1
const
maxn
=
400000
;
2
maxq
=
50000
;
3
var
s,l,r,n:
array
[
0
..maxn]
of
longint;
4
a:
array
[
1
..maxn]
of
longint;
5
ans,b,e,k,id:
array
[
0
..maxq]
of
longint;
6
last,m,q,i,j,t,tt:longint;
7
procedure
zig(
var
x:longint);
8
var
y:longint;
9
begin
10
y:
=
l[x]; l[x]:
=
r[y]; r[y]:
=
x;
11
s[y]:
=
s[x]; s[x]:
=
s[l[x]]
+
s[r[x]]
+
1
;
12
x:
=
y;
13
end
;
14
procedure
zag(
var
x:longint);
15
var
y:longint;
16
begin
17
y:
=
r[x]; r[x]:
=
l[y]; l[y]:
=
x;
18
s[y]:
=
s[x]; s[x]:
=
s[l[x]]
+
s[r[x]]
+
1
;
19
x:
=
y;
20
end
;
21
procedure
maintain(
var
x:longint; flag:boolean);
22
begin
23
if
flag
24
then
begin
25
if
s[l[l[x]]]
>
s[r[x]]
then
zig(x)
26
else
if
s[l[r[x]]]
>
s[r[x]]
27
then
begin
zag(l[x]); zig(x);
end
28
else
exit;
29
end
30
else
begin
31
if
s[r[r[x]]]
>
s[l[x]]
then
zag(x)
32
else
if
s[r[l[x]]]
>
s[l[x]]
33
then
begin
zig(r[x]); zag(x);
end
34
else
exit;
35
end
;
36
maintain(l[x],true); maintain(r[x],false);
37
maintain(x,true); maintain(x,false);
38
end
;
39
procedure
insert(
var
x:longint; v:longint);
40
begin
41
if
x
=
0
42
then
begin
43
inc(tt); x:
=
tt;
44
s[x]:
=
1
; n[x]:
=
v;
45
l[x]:
=
0
; r[x]:
=
0
;
46
end
47
else
begin
48
inc(s[x]);
49
if
v
<=
n[x]
50
then
insert(l[x],v)
51
else
insert(r[x],v);
52
maintain(x,v
<=
n[x]);
53
end
;
54
end
;
55
function
delete(
var
x:longint; v:longint):longint;
56
begin
57
if
x
=
0
then
exit;
58
dec(s[x]);
59
if
(l[x]
=
0
)
and
(v
<
n[x])
or
(r[x]
=
0
)
and
(v
>
n[x])
or
(v
=
n[x])
60
then
begin
61
delete:
=
n[x];
62
if
(l[x]
=
0
)
or
(r[x]
=
0
)
63
then
x:
=
l[x]
+
r[x]
64
else
n[x]:
=
delete(l[x],n[x]
+
1
);
65
end
66
else
if
v
<
n[x]
67
then
delete:
=
delete(l[x],v)
68
else
delete:
=
delete(r[x],v);
69
end
;
70
function
select(x,k:longint):longint;
71
begin
72
if
k
=
s[l[x]]
+
1
73
then
exit(n[x]);
74
if
k
<=
s[l[x]]
75
then
select:
=
select(l[x],k)
76
else
select:
=
select(r[x],k
-
s[l[x]]
-
1
);
77
end
;
78
procedure
sort(l,r:longint);
79
var
i,j,x,y:longint;
80
begin
81
i:
=
l; j:
=
r;
82
x:
=
b[(l
+
r)shr
1
];
83
repeat
84
while
b[i]
<
x
do
inc(i);
85
while
b[j]
>
x
do
dec(j);
86
if
not
(i
>
j)
87
then
begin
88
y:
=
b[i]; b[i]:
=
b[j]; b[j]:
=
y;
89
y:
=
e[i]; e[i]:
=
e[j]; e[j]:
=
y;
90
y:
=
k[i]; k[i]:
=
k[j]; k[j]:
=
y;
91
y:
=
id[i]; id[i]:
=
id[j]; id[j]:
=
y;
92
inc(i); dec(j);
93
end
;
94
until
i
>
j;
95
if
i
<
r
then
sort(i,r);
96
if
l
<
j
then
sort(l,j);
97
end
;
98
procedure
sortback(l,r:longint);
99
var
i,j,x,y:longint;
100
begin
101
i:
=
l; j:
=
r;
102
x:
=
id[(l
+
r)shr
1
];
103
repeat
104
while
id[i]
<
x
do
inc(i);
105
while
id[j]
>
x
do
dec(j);
106
if
not
(i
>
j)
107
then
begin
108
y:
=
b[i]; b[i]:
=
b[j]; b[j]:
=
y;
109
y:
=
e[i]; e[i]:
=
e[j]; e[j]:
=
y;
110
y:
=
k[i]; k[i]:
=
k[j]; k[j]:
=
y;
111
y:
=
id[i]; id[i]:
=
id[j]; id[j]:
=
y;
112
y:
=
ans[i]; ans[i]:
=
ans[j]; ans[j]:
=
y;
113
inc(i); dec(j);
114
end
;
115
until
i
>
j;
116
if
i
<
r
then
sortback(i,r);
117
if
l
<
j
then
sortback(l,j);
118
end
;
119
procedure
out(x:longint);
120
begin
121
if
x
=
0
then
exit;
122
out(l[x]);
123
write(n[x],
'
'
);
124
out(r[x]);
125
end
;
126
begin
127
assign(input,
'
feed.in
'
); reset(input);
128
assign(output,
'
feed.out
'
); rewrite(output);
129
readln(m,q);
130
for
i:
=
1
to
m
do
131
read(a[i]);
132
for
i:
=
1
to
q
do
133
begin
134
id[i]:
=
i;
135
readln(b[i],e[i],k[i]);
136
end
;
137
sort(
1
,q);
138
tt:
=
0
; t:
=
0
; s[
0
]:
=
0
;
139
b[
0
]:
=
0
; e[
0
]:
=
0
;
140
for
i:
=
1
to
q
do
141
begin
142
if
e[i
-
1
]
<
b[i]
143
then
begin
144
for
j:
=
b[i
-
1
]
to
e[i
-
1
]
do
145
delete(t,a[j]);
146
for
j:
=
b[i]
to
e[i]
do
147
insert(t,a[j]);
148
end
149
else
if
e[i
-
1
]
<
e[i]
150
then
begin
151
for
j:
=
b[i
-
1
]
to
b[i]
-
1
do
152
delete(t,a[j]);
153
for
j:
=
e[i
-
1
]
+
1
to
e[i]
do
154
insert(t,a[j]);
155
end
156
else
begin
157
for
j:
=
b[i
-
1
]
to
b[i]
-
1
do
158
delete(t,a[j]);
159
for
j:
=
e[i]
+
1
to
e[i
-
1
]
do
160
delete(t,a[j]);
161
end
;
162
ans[i]:
=
select(t,k[i]);
163
//
out(t);writeln
164
end
;
165
sortback(
1
,q);
166
for
i:
=
1
to
q
do
167
writeln(ans[i]);
168
close(input); close(output);
169
end
.
170
//大神的Splay 是yzhw写了之后 mq_miqing改成数组模拟指针的很不错
Splay
1
program
PKU_
2761
_Feed_the_dogs;
2
3
const
4
maxN
=
1000000
;
//
这里我开的10n过的，应该是多少我不清楚，望神牛解答
5
maxM
=
50000
;
6
7
type
8
TQuery
=
record
9
l,r,k,id:longint
10
end
;
11
12
var
13
n,m,root,numNode:longint;
14
a,left,right,fa,key,size:
array
[
0
..maxN]
of
longint;
15
q:
array
[
1
..maxM]
of
TQuery;
16
ans:
array
[
1
..maxM]
of
longint;
17
18
function
leftRotate(i:longint):longint;
19
var
20
j:longint;
21
begin
22
j:
=
right[i];
23
right[i]:
=
left[j];
24
left[j]:
=
i;
25
fa[j]:
=
fa[i];
26
fa[i]:
=
j;
27
if
right[i]
<>
0
then
fa[right[i]]:
=
i;
28
size[j]:
=
size[i];
29
size[i]:
=
size[left[i]]
+
size[right[i]]
+
1
;
30
exit(j);
31
end
;
32
33
function
rightRotate(i:longint):longint;
34
var
35
j:longint;
36
begin
37
j:
=
left[i];
38
left[i]:
=
right[j];
39
right[j]:
=
i;
40
fa[j]:
=
fa[i];
41
fa[i]:
=
j;
42
if
left[i]
<>
0
then
fa[left[i]]:
=
i;
43
size[j]:
=
size[i];
44
size[i]:
=
size[left[i]]
+
size[right[i]]
+
1
;
45
exit(j);
46
end
;
47
48
function
newNode(f,k:longint):longint;
49
begin
50
inc(numNode);
51
key[numNode]:
=
k;
52
fa[numNode]:
=
f;
53
size[numNode]:
=
1
;
54
exit(numNode);
55
end
;
56
57
procedure
splay(i:longint);
58
var
59
f,g:longint;
60
pg:^longint;
61
begin
62
while
fa[i]
<>
0
do
begin
63
f:
=
fa[i];
64
g:
=
fa[f];
65
if
g
=
0
then
begin
66
if
i
=
left[f]
then
root:
=
rightRotate(f)
67
else
root:
=
leftRotate(f);
68
break;
69
end
;
70
if
fa[g]
=
0
then
pg:
=
@root
71
else
if
g
=
left[fa[g]]
then
pg:
=
@left[fa[g]]
72
else
pg:
=
@right[fa[g]];
73
if
f
=
left[g]
then
begin
74
if
i
=
left[f]
then
begin
75
pg^:
=
rightRotate(g);
76
pg^:
=
rightRotate(f);
77
end
else
begin
78
left[g]:
=
leftRotate(f);
79
pg^:
=
rightRotate(g);
80
end
;
81
end
else
begin
82
if
i
=
right[f]
then
begin
83
pg^:
=
leftRotate(g);
84
pg^:
=
leftRotate(f);
85
end
else
begin
86
right[g]:
=
rightRotate(f);
87
pg^:
=
leftRotate(g);
88
end
;
89
end
;
90
end
;
91
end
;
92
93
procedure
insert(k:longint);
94
var
95
i,j:longint;
96
begin
97
if
root
=
0
then
begin
98
root:
=
newNode(
0
,k);
99
exit;
100
end
;
101
i:
=
root;
102
inc(size[root]);
103
if
k
<
key[i]
then
j:
=
left[i]
else
j:
=
right[i];
104
while
j
<>
0
do
begin
105
inc(size[j]);
106
i:
=
j;
107
if
k
<
key[j]
then
j:
=
left[j]
else
j:
=
right[j];
108
end
;
109
if
k
<
key[i]
then
begin
110
left[i]:
=
newNode(i,k);
111
splay(left[i]);
112
end
else
begin
113
right[i]:
=
newNode(i,k);
114
splay(right[i]);
115
end
;
116
end
;
117
118
function
union(a,b:longint):longint;
119
var
120
i,j:longint;
121
begin
122
i:
=
a;
123
while
right[i]
<>
0
do
i:
=
right[i];
124
splay(i);
125
j:
=
b;
126
while
left[j]
<>
0
do
j:
=
left[j];
127
splay(j);
128
fa[i]:
=
j;
129
inc(size[j],size[i]);
130
left[j]:
=
i;
131
exit(j);
132
end
;
133
134
procedure
delete(k:longint);
135
var
136
i,l,r:longint;
137
begin
138
i:
=
root;
139
while
key[i]
<>
k
do
140
if
k
<
key[i]
then
i:
=
left[i]
else
i:
=
right[i];
141
splay(i);
142
if
(left[i]
=
0
)
and
(right[i]
=
0
)
then
root:
=
0
143
else
if
left[i]
=
0
then
begin
root:
=
right[i]; fa[right[i]]:
=
0
;
end
144
else
if
right[i]
=
0
then
begin
root:
=
left[i]; fa[left[i]]:
=
0
;
end
145
else
begin
146
l:
=
left[i]; r:
=
right[i];
147
fa[l]:
=
0
; fa[r]:
=
0
; root:
=
0
;
148
root:
=
union(l,r);
149
end
;
150
key[i]:
=-
1
;
151
end
;
152
153
function
select(k:longint):longint;
154
var
155
i:longint;
156
begin
157
i:
=
root;
158
while
k
<>
size[left[i]]
+
1
do
159
if
k
<
size[left[i]]
+
1
then
i:
=
left[i]
else
begin
160
dec(k,size[left[i]]
+
1
);
161
i:
=
right[i];
162
end
;
163
exit(key[i]);
164
end
;
165
166
function
lessThan(
var
a,b:TQuery):boolean;
167
begin
168
if
a.l
<
b.l
then
exit(true)
169
else
if
a.l
>
b.l
then
exit(false)
170
else
if
a.r
>
b.r
then
exit(true)
171
else
exit(false);
172
end
;
173
174
procedure
qSort(l,r:longint);
175
var
176
i,j:longint;
177
x,tmp:TQuery;
178
begin
179
i:
=
l; j:
=
r; x:
=
q[(i
+
j)
>>
1
];
180
repeat
181
while
lessThan(q[i],x)
do
inc(i);
182
while
lessThan(x,q[j])
do
dec(j);
183
if
i
<=
j
then
begin
184
tmp:
=
q[i]; q[i]:
=
q[j]; q[j]:
=
tmp;
185
inc(i); dec(j);
186
end
;
187
until
i
>
j;
188
if
i
<
r
then
qSort(i,r);
189
if
j
>
l
then
qSort(l,j);
190
end
;
191
192
procedure
init;
193
var
194
i:longint;
195
begin
196
assign(input,
'
kth.in
'
); reset(input);
197
assign(output,
'
kth.out
'
); rewrite(output);
198
readln(n,m);
199
for
i:
=
1
to
n
do
read(a[i]);
200
readln;
201
for
i:
=
1
to
m
do
202
with
q[i]
do
begin
203
readln(l,r,k);
204
id:
=
i;
205
end
;
206
qSort(
1
,m);
207
end
;
208
209
function
max(a,b:longint):longint;
210
begin
if
a
>
b
then
exit(a)
else
exit(b);
end
;
211
212
function
min(a,b:longint):longint;
213
begin
if
a
<
b
then
exit(a)
else
exit(b);
end
;
214
215
procedure
main;
216
var
217
i,j:longint;
218
begin
219
for
j:
=
q[
1
].l
to
q[
1
].r
do
220
insert(a[j]);
221
ans[q[
1
].id]:
=
select(q[
1
].k);
222
for
i:
=
2
to
m
do
begin
223
if
q[i].l
>
q[i
-
1
].r
then
begin
224
for
j:
=
q[i
-
1
].l
to
q[i
-
1
].r
do
delete(a[j]);
225
for
j:
=
q[i].l
to
q[i].r
do
insert(a[j]);
226
end
else
if
(q[i].l
<=
q[i
-
1
].r)
and
(q[i].r
>
q[i
-
1
].r)
then
begin
227
for
j:
=
q[i
-
1
].r
+
1
to
q[i].r
do
insert(a[j]);
228
for
j:
=
q[i
-
1
].l
to
q[i].l
-
1
do
delete(a[j]);
229
end
else
begin
230
for
j:
=
q[i
-
1
].l
to
q[i].l
-
1
do
delete(a[j]);
231
for
j:
=
q[i].r
+
1
to
q[i
-
1
].r
do
delete(a[j]);
232
end
;
233
ans[q[i].id]:
=
select(q[i].k);
234
end
;
235
end
;
236
237
procedure
print;
238
var
239
i:longint;
240
begin
241
for
i:
=
1
to
m
do
writeln(ans[i]);
242
end
;
243
244
begin
245
init;
246
main;
247
print;
248
close(input); close(output);
249
end
.
一题多练是很爽的啊
p.s. SBT确实快1700+ms Splay是3000+ms 看来Splay树的优越性确实不在作为平衡树使用
换句话说 拿Splay和其他平衡树比较是相当不公平不合理的 发扬光大Splay独有的Splay操作才是硬道理
BOB HAN原创 转载请注明出处