poj2528
线段树，线段树一般是对连续的区块进行操作，每次给出相应的区块，但是本题给出海报覆盖的是区间，要把区间对应到区块上。虽然有些情况还不能处理，但是过了。
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#include
<
iostream
>
#include
<
cstdio
>
#include
<
cstdlib
>
#include
<
cstring
>
#include
<
algorithm
>
using
namespace
std;
#define
maxn 20005
struct
Interval
{
int
s, e;
}interval[maxn];
struct
Node
{
Node
*
pleft,
*
pright;
int
l, r;
bool
full;
}tree[maxn
*
3
];
int
pos[maxn
*
2
], poscount, ncount;
void
buildtree(Node
*
proot,
int
l,
int
r)
{
proot
->
l
=
l;
proot
->
r
=
r;
if
(l
==
r)
return
;
int
mid
=
(l
+
r)
/
2
;
ncount
++
;
proot
->
pleft
=
tree
+
ncount;
ncount
++
;
proot
->
pright
=
tree
+
ncount;
buildtree(proot
->
pleft, l, mid);
buildtree(proot
->
pright, mid
+
1
, r);
}
bool
paste(Node
*
proot,
int
l,
int
r)
{
if
(l
==
r)
return
false
;
if
(proot
->
full)
return
false
;
if
(proot
->
l
==
l
&&
proot
->
r
==
r
-
1
)
{
proot
->
full
=
true
;
return
true
;
}
int
mid
=
(proot
->
l
+
proot
->
r)
/
2
;
bool
ret;
if
(r
<=
mid
+
1
)
ret
=
paste(proot
->
pleft, l, r);
else
if
(l
>
mid)
ret
=
paste(proot
->
pright, l, r);
else
{
ret
=
paste(proot
->
pleft, l, mid
+
1
);
ret
=
paste(proot
->
pright, mid
+
1
, r)
||
ret;
}
proot
->
full
=
proot
->
pleft
->
full
&&
proot
->
pright
->
full;
return
ret;
}
int
binarysearch(
int
a)
{
int
l
=
0
;
int
r
=
poscount
-
1
;
while
(l
<
r)
{
int
mid
=
(l
+
r)
/
2
;
if
(pos[mid]
>=
a)
r
=
mid;
else
l
=
mid
+
1
;
}
return
l;
}
int
main()
{
//
freopen("t.txt", "r", stdin);
int
t;
scanf(
"
%d
"
,
&
t);
while
(t
--
)
{
poscount
=
0
;
ncount
=
0
;
memset(tree,
0
,
sizeof
(tree));
int
n;
scanf(
"
%d
"
,
&
n);
for
(
int
i
=
0
; i
<
n; i
++
)
{
scanf(
"
%d%d
"
,
&
interval[i].s,
&
interval[i].e);
pos[poscount
++
]
=
interval[i].s;
pos[poscount
++
]
=
interval[i].e;
}
sort(pos, pos
+
poscount);
poscount
=
unique(pos, pos
+
poscount)
-
pos;
buildtree(tree,
0
, poscount
-
1
);
int
ans
=
0
;
for
(
int
i
=
n
-
1
; i
>=
0
; i
--
)
{
int
s
=
binarysearch(interval[i].s);
int
e
=
binarysearch(interval[i].e)
+
1
;
if
(paste(tree, s, e))
ans
++
;
}
printf(
"
%d\n
"
, ans);
}
return
0
;
}