1207: Problem D: Knight’s Trip

题目描述

Problem D: Knight's Trip
In chess, each move of a knight consists of moving by two squares horizontally and one square vertically, or by one square horizontally and two squares vertically. A knight making one move from location (0,0) of an infinite chess board would end up at one of the following eight locations: (1,2), (-1,2), (1,-2), (-1,-2), (2,1), (-2,1), (2,-1), (-2,-1).
Starting from location (0,0), what is the minimum number of moves required for a knight to get to some other arbitrary location (x,y)?

输入

Each line of input contains two integers x and y, each with absolute value at most one billion. The integers designate a location (x,y) on the infinite chess board. The final line contains the word END.

输出

For each location in the input, output a line containing one integer, the minimum number of moves required for a knight to move from (0,0) to (x, y).

样例输入

1 2
2 4
END

样例输出

1
2

参考代码

#include <stdio.h>
#include <math.h>
int n;
double x[1000], y[1000], r[1000];
int top[1000];
int possible = 1;
double ne = 1000, nw = 1000;
main() 
{
    int i,j,k;
    scanf("%d",&n);
    for (i=0;i<n;i++) scanf("%lf%lf%lf",&x[i],&y[i],&r[i]);
    for (i=0;i<n;i++) if (y[i]+r[i] > 1000) visit(i);
    /*
   if (possible) printf(
     "Bill enters at (0.00, %0.2lf) and leaves at (1000.00, %0.2lf).n",nw,ne);
   else printf("Bill will be bitten.n");
   */
    if (possible) printf(
         "0.00 %0.2lf 1000.00 %0.2lfn",nw,ne);
   else printf("IMPOSSIBLEn");
}
visit(int i){
   int j,k;
   double yy;
   if (top[i]++) return;
   for (j=0;j<n;j++) {
      if (hypot(x[j]-x[i],y[j]-y[i]) < r[i]+r[j]) visit(j);
   }
   if (y[i]-r[i] < 0) possible = 0;
   if (x[i]-r[i] < 0) {
      yy = y[i] - sqrt(r[i]*r[i] - x[i]*x[i]);
      if (yy < nw) nw = yy;
   }
   if (x[i]+r[i] > 1000) {
      yy = y[i] - sqrt(r[i]*r[i] - (1000-x[i])*(1000-x[i]));
      if (yy < ne) ne = yy;
   }
}

解析

暂无