Szucoder Round #4 (div.2)

地址：http://codeforces.com/problemset/problem/486/A

A. Calculating Function
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standardoutput
For apositive integer n let's define a function f:

f(n) =  - 1 + 2 - 3 + .. + ( - 1)nn

Your task isto calculate f(n) for a given integer n.

Input

The singleline contains the positive integer n (1 ≤ n ≤ 1015).

Output

Print f(n) in asingle line.

Sample test(s)

input

4
output

2
input

5
output

-3
Note

f(4) =  - 1 + 2 - 3 + 4 = 2

f(5) =  - 1 + 2 - 3 + 4 - 5 =  - 3

思路：
一开始真的模拟加减法，导致因数据太大而超时。顿时反应过来错误。

比赛时程序：
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <algorithm>
using namespace std;

int main()
{
__int64 n;

scanf("%I64d",&n);

if (n%2==0)
printf("%I64d\n",n/2);
else
printf("%I64d\n",-1*n/2-1);
return 0;
}

地址：http://codeforces.com/problemset/problem/475/A

A. Bayan Bus
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standardoutput
The finalround of Bayan Programming Contest will be held in Tehran, and the participantswill be carried around with a yellow bus. The bus has 34 passenger seats: 4seats in the last row and 3 seats in remaining rows.

The eventcoordinator has a list of k participants who should be picked up atthe airport. When a participant gets on the bus, he will sit in the last
rowwith an empty seat. If there is more than one empty seat in that row, he willtake the leftmost one.

In order tokeep track of the people who are on the bus, the event coordinator needs afigure showing which seats are going to be taken by k participants.Your
task is to draw the figure representing occupied seats.

Input

The only lineof input contains integer k, (0 ≤ k ≤ 34), denoting the
number ofparticipants.

Output

Print thefigure of a bus with k passengers as described in sample tests.Character '#'
denotes anempty seat, while 'O' denotes ataken seat. 'D' is the busdriver and other characters in the output are for
the purpose of beautifyingthe figure. Strictly follow the sample test cases output format. Print exactlysix lines. Do not output extra space or other characters.

Sample test(s)

input

9
output

+------------------------+

|O.O.O.#.#.#.#.#.#.#.#.|D|)

|O.O.O.#.#.#.#.#.#.#.#.|.|

|O.......................|

|O.O.#.#.#.#.#.#.#.#.#.|.|)

+------------------------+
input

20
output

+------------------------+

|O.O.O.O.O.O.O.#.#.#.#.|D|)

|O.O.O.O.O.O.#.#.#.#.#.|.|

|O.......................|

|O.O.O.O.O.O.#.#.#.#.#.|.|)

+------------------------+

思路：
找规律，排除特殊情况。

比赛时程序：
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <algorithm>
using namespace std;

void pr(int);

int main()
{
int n;
scanf("%d",&n);
printf("+------------------------+\n|");
if (n>0)
pr((n-2)/3+1);
else pr(0);
printf("|D|)\n|");
if (n<3)
pr((n+1)/3);
else
pr(n/3);
printf("|.|\n");
if (n<3) printf("|#.......................|\n|");
else printf("|O.......................|\n|");
pr((n-1)/3);
printf("|.|)\n");
printf("+------------------------+\n");
return 0;
}

void pr(int n)
{
int i;
for (i=1;i<=n;i++)
printf("O.");
for (i=1;i<=11-n;i++)
printf("#.");
}

地址：http://codeforces.com/problemset/problem/492/B

B. Vanya and Lanterns
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standardoutput
Vanya walkslate at night along a straight street of length l, lit by n lanterns.Consider
the coordinate system with the beginning of the street correspondingto the point 0, and its endcorresponding to the point l.
Then the i-th lanternis at the point ai. The lantern
lights allpoints of the street that are at the distance of at most d fromit, where d is somepositive
number, common for all lanterns.

Vanyawonders: what is the minimum light radius d shouldthe lanterns have to light the whole street?

Input

The firstline contains two integers n, l (1 ≤ n ≤ 1000, 1 ≤ l ≤ 109) —
thenumber of lanterns and the length of the street respectively.

The next linecontains n integers ai (0 ≤ ai ≤ l).
Multiplelanterns can be located at the same point. The lanterns may be located at theends of the street.

Output

Print theminimum light radius d, needed to light the whole street. The answer will beconsidered correct if its absolute or relative error doesn't exceed 10 - 9.

Sample test(s)

input

7 15

15 5 3 7 9 14 0
output

2.5000000000
input

2 5

2 5
output

2.0000000000
Note

Consider thesecond sample. At d = 2 the first lantern will light the segment [0, 4] of
thestreet, and the second lantern will light segment[3, 5]. Thus, thewhole street will be lit.

思路：
输入时去重，然后排序，算出任意相邻两盏灯间的半径，路的两端特殊处理，最后找出最大值。

比赛时程序：
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <algorithm>
using namespace std;

int main()
{
int n,l,a[1005],len,i,temp;
double min,r;

memset(a,0,sizeof(a));

scanf("%d%d",&n,&l);

map<int,int> point;
len=1;
a[0]=0;
for (i=1;i<=n;i++)
{
scanf("%d",&temp);
if (!point[temp]++)
a[len++]=temp;
}
if (!point[l])
a[len++]=l;

sort(a,a+len);

if (!point[0])
min=a[1]-a[0];
else
min=0;
for (i=0;i<len-1;i++)
{
r=(a[i+1]-a[i])/2.0;
if (r>min) min=r;
}
if (!point[l] && a[len-1]-a[len-2]>min) min=a[len-1]-a[len-2];
printf("%12.10lf\n",min);
return 0;
}

地址：http://codeforces.com/problemset/problem/489/B

B. BerSU Ball
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standardoutput
The BerlandState University is hosting a ballroom dance in celebration of its 100500-thanniversary! n boys and m girlsare
already busy rehearsing waltz, minuet, polonaise and quadrille moves.

We know thatseveral boy&girl pairs are going to be invited to the ball. However, thepartners' dancing skill in each pair must differ by at most one.

For each boy,we know his dancing skills. Similarly, for each girl we know her dancingskills. Write a code that can determine the largest possible number of pairs thatcan be formed from n boys
and m girls.

Input

The firstline contains an integer n (1 ≤ n ≤ 100) — the number of boys.
Thesecond line contains sequence a1, a2, ..., an (1 ≤ ai ≤ 100),
where ai is the i-th boy'sdancing skill.

Similarly,the third line contains an integer m (1 ≤ m ≤ 100) — thenumber
of girls. The fourth line contains sequence b1, b2, ..., bm (1 ≤ bj ≤ 100),
where bj is the j-th girl'sdancing skill.

Output

Print asingle number — the required maximum possible number of pairs.

Sample test(s)

input

4

1 4 6 2

5

5 1 5 7 9
output

3
input

4

1 2 3 4

4

10 11 12 13
output

0
input

5

1 1 1 1 1

3

1 2 3
output

2

思路：
贪心，先把男女分别排序，从skill最小的两个开始尝试配对，配对不成功的时候skill小的下标加一。

比赛时程序：
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <algorithm>
using namespace std;

int main()
{
int a[105],b[105];
int n,i,j,m,sum;

memset(a,0,sizeof(a));
memset(b,0,sizeof(b));

scanf("%d",&n);
for (i=0;i<n;i++)
scanf("%d",&a[i]);

scanf("%d",&m);
for (i=0;i<m;i++)
scanf("%d",&b[i]);

sort(a,a+n);
sort(b,b+m);

i=0;
j=0;
sum=0;
while (i<n && j<m)
{
if (abs(a[i]-b[j])<=1)
{
sum++;
i++;
j++;
}
else
{
if (a[i]>b[j]) j++;
else i++;
}
}

printf("%d\n",sum);

return 0;
}