Stars
Description
Astronomers often examine star maps where stars
are represented by points on a plane and each star has Cartesian
coordinates. Let the level of a star be an amount of the stars that are
not higher and not to the right of the given star. Astronomers want to
know the distribution of the levels of the stars.
For example, look at the map shown on the figure above. Level of the
star number 5 is equal to 3 (it's formed by three stars with a numbers
1, 2 and 4). And the levels of the stars numbered by 2 and 4 are 1. At
this map there are only one star of the level 0, two stars of the level
1, one star of the level 2, and one star of the level 3.
You are to write a program that will count the amounts of the stars
of each level on a given map.
Input
The first line of the input file contains a
number of stars N (1<=N<=15000). The following N lines describe
coordinates of stars (two integers X and Y per line separated by a
space, 0<=X,Y<=32000). There can be only one star at one point of
the plane. Stars are listed in ascending order of Y coordinate. Stars
with equal Y coordinates are listed in ascending order of X coordinate.
Output
The
output should contain N lines, one number per line. The first line
contains amount of stars of the level 0, the second does amount of stars
of the level 1 and so on, the last line contains amount of stars of the
level N-1.
Sample Input
5
1 1
5 1
7 1
3 3
5 5
Sample Output
1
2
1
1
0
题意:某星左下方的星数为它的值。求出值从0到n-1的星数。
代码:
#include
<
stdio.h
>
#define
maxn 32010
int
c[maxn], sum[maxn];
int
lowBit(
int
x)
{
return
x
&
(x
^
(x
-
1
));//return x & (-x);更快
}
void
update(
int
x)
{
while
(x
<
maxn)
{
c[x]
++
;
x
+=
lowBit(x);
}
}
int
s(
int
x)
{
int
pre
=
0
;
while
(x
>
0
)
{
pre
+=
c[x];
x
-=
lowBit(x);
}
return
pre;
}
int
main()
{
int
i, n, x, y;
scanf(
"
%d
"
,
&
n);
for
(i
=
0
; i
<
n; i
++
)
{
scanf(
"
%d%d
"
,
&
x,
&
y);
//
树状数组的坐标是从1开始
sum[s(x
+
1
)]
++
;
update(x
+
1
);
}
for
(i
=
0
; i
<
n; i
++
)
{
printf(
"
%d\n
"
, sum[i]);
}
system(
"
pause
"
);
return
0
;
}