1、http://codeforces.com/contest/404/problem/B
2、题目大意：
马拉松运动员在一个a*a的举证沿着逆时针跑，每隔d米就喝一瓶水，求每次喝水的坐标，题目不难，但是比赛的时候一直wrong 在第八组样例，应该是乘除影响到了精度问题
3、题目：
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 equals nd?+?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.
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.
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.
2 5 2
1.0000000000 2.0000000000 2.0000000000 0.0000000000
4.147 2.8819 6
2.8819000000 0.0000000000 4.1470000000 1.6168000000 3.7953000000 4.1470000000 0.9134000000 4.1470000000 0.0000000000 2.1785000000 0.7034000000 0.00000000004、wrong 在第八组的代码：
#include<stdio.h>
#include<math.h>
#include<string.h>
#include<algorithm>
using namespace std;
int main()
{double n;double a,d;double error=0.0001;while(scanf("%lf%lf",&a,&d)!=EOF){double x=0.0;scanf("%lf",&n);for(double i=1.0;i<=n;i+=1.0){int tmp=(int)((d*i)/a);double ans=fabs(d*i-a*tmp*1.0)<=error?x:d*i-a*tmp*1.0;tmp=tmp%4;if(ans>0){if(tmp==0){printf("%.10f %.10f\n",ans,x);}else if(tmp==1){printf("%.10f %.10f\n",a,ans);}else if(tmp==2){printf("%.10f %.10f\n",fabs(a-ans)<=error?x:a-ans,a);}else if(tmp==3){printf("%.10f %.10f\n",x,fabs(a-ans)<=error?x:a-ans);}}else if(ans==0){if(tmp==0){printf("%.10f %.10f\n",x,x);}else if(tmp==1){printf("%.10f %.10f\n",a,x);}else if(tmp==2){printf("%.10f %.10f\n",a,a);}else if(tmp==3){printf("%.10f %.10f\n",x,a);}}}}return 0;
}
/*
1 1.6888
2
10000 10000
10000
*/
队友AC的代码：
#include<stdio.h>
int main()
{double a,d,posx,posy,dd;int n,con;while(scanf("%lf%lf%d",&a,&dd,&n)!=EOF){//1右2上3左4下con=1;posx=posy=0;while(dd>=4*a)dd-=4*a;d=dd;while(n--){switch(con){case 1:{if(posx+d<=a){posx+=d;printf("%.10f %.10f\n",posx,posy);d=dd;}else{d-=a-posx;posx=a;n++;con++;}break;}case 2:{if(posy+d<=a){posy+=d;printf("%.10f %.10f\n",posx,posy);d=dd;}else{d-=a-posy;posy=a;n++;con++;}break;}case 3:{if(posx-d>=0){posx-=d;printf("%.10f %.10f\n",posx,posy);d=dd;}else{d-=posx;posx=0;n++;con++;}break;}case 4:{if(posy-d>=0){posy-=d;printf("%.10f %.10f\n",posx,posy);d=dd;}else{d-=posy;posy=0;n++;con=1;}break;}}}}return 0;
}