Codeforce237-Div.2 A,B

A. Valera and X

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Valera is a little boy. Yesterday he got a huge Math hometask at school, so Valera didn't have enough time to properly learn the English alphabet for his English lesson. Unfortunately, the English teacher decided to have a test on alphabet today. At the test Valera got a square piece of squared paper. The length of the side equals n squares (n is an odd number) and each unit square contains some small letter of the English alphabet.

Valera needs to know if the letters written on the square piece of paper form letter "X". Valera's teacher thinks that the letters on the piece of paper form an "X", if:

• on both diagonals of the square paper all letters are the same;
• all other squares of the paper (they are not on the diagonals) contain the same letter that is different from the letters on the diagonals.

Help Valera, write the program that completes the described task for him.

Input

The first line contains integer n (3 ≤ n < 300; n is odd). Each of the next n lines contains n small English letters — the description of Valera's paper.

Output

Print string "YES", if the letters on the paper form letter "X". Otherwise, print string "NO". Print the strings without quotes.

Sample test(s)

input

5xoooxoxoxosoxoooxoxoxooox

output

NO

input

3wswswswsw

output

YES

input

3xpxpxpxpe

output

NO

题意:判断所给的字符是否可以形成X型...

思路:比赛的时候一直忽视了X上的字母和X外的字母不能一致...要提高思维严谨性

CODE:

#include<stdio.h>#include<iostream>#include<string.h>using namespace std;char a[305][305];bool test1(int nn){    char a1,a2;    a1=a[0][0];    a2=a[nn-1][nn-1];    for(int i=0;i<nn;i++)    {        if(a1!=a[i][i]) return false;    }    for(int i=0,j=nn-1;i<nn;i++,j--)    {        if(a2!=a[i][j]) return false;    }    return true;}bool test2(int nn){    char t=a[0][1];    for(int i=0;i<nn;i++)        for(int j=0;j<nn;j++)    {        if(i==j||(i+j)==(nn-1))            continue;        else if(t!=a[i][j]) return false;    }    return true;}int main(){    //freopen("A.txt","r",stdin);    int n;    while(~scanf("%d",&n))    {        for(int i=0;i<n;i++)        {            scanf("%s",a[i]);            getchar();        }        if(a[0][0]!=a[0][1]&&test1(n)&&test2(n)) printf("YES\n");        else printf("NO\n");    }    return 0;}

B. Marathon

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Valera takes part in the Berland Marathon. The marathon race starts at the stadium that can be represented on the plane as a square whose lower left corner is located at point with coordinates (0, 0) and the length of the side equals a meters. The sides of the square are parallel to coordinate axes.

As the length of the marathon race is very long, Valera needs to have extra drink during the race. The coach gives Valera a bottle of drink each d meters of the path. We know that Valera starts at the point with coordinates (0, 0) and runs counter-clockwise. That is, when Valera covers a meters, he reaches the point with coordinates (a, 0). We also know that the length of the marathon race equalsnd + 0.5 meters.

Help Valera's coach determine where he should be located to help Valera. Specifically, determine the coordinates of Valera's positions when he covers d, 2·d, ..., n·d meters.

Input

The first line contains two space-separated real numbers a and d (1 ≤ a, d ≤ 105), given with precision till 4 decimal digits after the decimal point. Number a denotes the length of the square's side that describes the stadium. Number d shows that after each d meters Valera gets an extra drink.

The second line contains integer n (1 ≤ n ≤ 105) showing that Valera needs an extra drink n times.

Output

Print n lines, each line should contain two real numbers xi and yi, separated by a space. Numbers xi and yi in the i-th line mean that Valera is at point with coordinates (xi, yi) after he covers i·d meters. Your solution will be considered correct if the absolute or relative error doesn't exceed 10 - 4.

Note, that this problem have huge amount of output data. Please, do not use cout stream for output in this problem.

Sample test(s)

input

2 52

output

1.0000000000 2.00000000002.0000000000 0.0000000000

input

4.147 2.88196

output

2.8819000000 0.00000000004.1470000000 1.61680000003.7953000000 4.14700000000.9134000000 4.14700000000.0000000000 2.17850000000.7034000000 0.0000000000

题意:绕矩形外围跑,每过一段距离给一杯水,求出每个一杯水人所在的坐标..

思路:新技能:对浮点数取模 float fmod(float a,flaot b) %只能对int取模

CODE:

#include<stdio.h>#include<iostream>#include<string.h>#include<math.h>using namespace std;#define maxx 100005double aa[maxx][2];int main(){    //freopen("B.txt","r",stdin);    double a,d;    int n;    while(~scanf("%lf%lf",&a,&d))    {        int j=0;        scanf("%d",&n);        for(int i=1;i<=n;i++)        {            double k=i*d;            double kk=fmod(k,4*a);            int t=(int)(kk/a);            if(t==0)            {                aa[j][1]=0.0;aa[j][0]=kk; j++;            }            if(t==1)            {                aa[j][0]=a;aa[j][1]=kk-t*a;j++;            }            if(t==2)            {                aa[j][1]=a;aa[j][0]=a-(kk-t*a);j++;            }            if(t==3)            {                aa[j][0]=0.0;aa[j][1]=a-(kk-t*a);j++;            }        }        for(int i=0;i<n;i++)        {           printf("%.4lf000000 %.4lf000000\n",aa[i][0],aa[i][1]);        }    }    return 0;}