UVA 10065 Useless Tile Packers
水题，求个面积，再求个凸包的面积，减一下除以凸包面积即可。
复制的时候 多复制了个空格，PE了次。。以为是换行问题，改了下WA了。。。后来才看到。。。看来复制输出也要小心啊。。
#include <queue> #include <stack> #include <math.h> #include <stdio.h> #include <stdlib.h> #include <iostream> #include <limits.h> #include <string.h> #include <string> #include <algorithm> using namespace std; const int MAX = 110; struct point{double x,y;}; point c[MAX]; const double eps = 1e-6; bool dy(double x,double y) { return x > y + eps;} // x > y bool xy(double x,double y) { return x < y - eps;} // x < y bool dyd(double x,double y) { return x > y - eps;} // x >= y bool xyd(double x,double y) { return x < y + eps;} // x <= y bool dd(double x,double y) { return fabs( x - y ) < eps;} // x == y double crossProduct(point a,point b,point c)//向量 ac 在 ab 的方向 { return (c.x - a.x)*(b.y - a.y) - (b.x - a.x)*(c.y - a.y); } double disp2p(point a,point b) { return sqrt( ( a.x - b.x ) * ( a.x - b.x ) + ( a.y - b.y ) * ( a.y - b.y ) ); } bool cmp(point a,point b) // 排序 { double len = crossProduct(c[0],a,b); if( dd(len,0.0) ) return xy(disp2p(c[0],a),disp2p(c[0],b)); return xy(len,0.0); } point stk[MAX]; int top; void Graham(point c[],int n) { int tmp = 0; for(int i=1; i<n; i++) if( xy(c[i].x,c[tmp].x) || dd(c[i].x,c[tmp].x) && xy(c[i].y,c[tmp].y) ) tmp = i; swap(c[0],c[tmp]); sort(c+1,c+n,cmp); stk[0] = c[0]; stk[1] = c[1]; top = 1; for(int i=2; i<n; i++) { while( xyd( crossProduct(stk[top],stk[top-1],c[i]), 0.0 ) && top >= 1 ) top--; stk[++top] = c[i]; } } double area_polygon(point p[],int n) { double s = 0.0; for(int i=0; i<n; i++) s += p[(i+1)%n].y * p[i].x - p[(i+1)%n].x * p[i].y; return fabs(s)/2.0; } int main() { int n; int ind = 1; while( ~scanf("%d",&n) && n ) { for(int i=0; i<n; i++) scanf("%lf%lf",&c[i].x,&c[i].y); double area_min = area_polygon(c,n); Graham(c,n); double area_max = area_polygon(stk,top+1); printf("Tile #%d/nWasted Space = %.2lf %%/n/n",ind++,(area_max-area_min)/area_max*100); } return 0; }