Zoj 3107 counting squares // computational ry

Draw a polygon according to the instruction and find the number of squares in it.

Idea: Obtain the area. Note: You need to determine the direction of a polygon and use the plus and minus numbers of the cross product.

#include<iostream>#include<stdio.h>#include<math.h>#include<string.h>int dir[][4]={{0,1},{0,-1},{-1,0},{1,0}};int f(char ch ){if(ch=='U') return 0;else if(ch=='D') return 1;else if(ch=='L') return 2;return 3;}class node{public:int x,y;};node st[150],ld,py[150];using namespace std;int n,ind;bool judge(){int an1=0,an2=0;for(int i=2;i<n;i++){node p0= py[i-1],p1=py[i],p2=py[(i+1)%n];int x0= p2.x -p1.x ,y0=p2.y -p1.y ;    int x1= p1.x -p0.x ,y1=p1.y -p0.y ;int k=(x0*y1-x1*y0);if(k>0) an1++;if(k<0) an2++;}if(an1>an2) return true;return false;}void work(){if(judge()){int k=n;for(int i=1;i<=k/2;i++){node temp =py[i];py[i]=py[k-i];py[k-i]=temp;}}int s=0;s=py[0].y *(py[n-1].x -py[1].x );for(int i=1;i<n;i++)s+=py[i].y *(py[i-1].x -py[(i+1)%n].x );printf("%d\n",s/2);}int main(){int t;int i=0;int ca=0;scanf("%d",&t);while(t--){char s[120];scanf("%s",s);int len=strlen(s);st[0].x =0;st[0].y =0;ld=st[0];ind =0;for(i=0;i<len;i++){int k=f(s[i]);st[i+1].x =st[i].x +dir[k][0];st[i+1].y =st[i].y +dir[k][1];if(st[i+1].x <ld.x ) ld=st[i+1],ind=i+1;if(st[i+1].x ==ld.x &&st[i+1].y <ld.y ) ld=st[i+1],ind=i+1;}n=i;int j=1;i=ind;while(j<=n){py[j-1]=st[i%n];j++,i++;}printf("case %d: ",++ca);work();}return 0;}