http://poj.org/problem?id=1151
想学一下扫描线线段树，结果写了道水题。
1 #include<iostream> 2 #include<cstdio> 3 #include<algorithm> 4 #include<cstring> 5 #include<cmath> 6 #include<set> 7 using namespace std; 8 const int maxn=110; 9 int n; 10 double a1[maxn][4]; 11 int a[maxn][4]; 12 double b[maxn*4],c[maxn*2]; 13 int tot=0,tot1=0; 14 int main(){ 15 for(int T=1;;T++){ 16 scanf("%d",&n); 17 if(n==0)break; 18 tot=0,tot1=0; 19 for(int i=1;i<=n;i++){ 20 scanf("%lf%lf%lf%lf",&a1[i][0],&a1[i][1],&a1[i][2],&a1[i][3]); 21 b[++tot]=a1[i][0];b[++tot]=a1[i][2]; 22 c[++tot1]=a1[i][1];c[++tot1]=a1[i][3]; 23 } 24 sort(b+1,b+1+tot);sort(c+1,c+1+tot1); 25 tot=unique(b+1,b+1+tot)-b-1; 26 tot1=unique(c+1,c+1+tot1)-c-1; 27 for(int i=1;i<=n;i++){ 28 a[i][0]=lower_bound(b+1,b+1+tot,a1[i][0])-b; 29 a[i][1]=lower_bound(c+1,c+1+tot1,a1[i][1])-c; 30 a[i][2]=lower_bound(b+1,b+1+tot,a1[i][2])-b; 31 a[i][3]=lower_bound(c+1,c+1+tot1,a1[i][3])-c; 32 }double ans=0; 33 for(int i=1;i<tot;i++){ 34 for(int j=1;j<tot1;j++){ 35 int f=0; 36 for(int z=1;z<=n;z++){ 37 if(i+1<=a[z][2]&&i>=a[z][0]&&j+1<=a[z][3]&&j>=a[z][1]){ 38 f=1;break; 39 } 40 } 41 if(f){ 42 ans+=(b[i+1]-b[i])*(c[j+1]-c[j]); 43 } 44 } 45 } 46 printf("Test case #%d ",T); 47 printf("Total explored area: %.2f ",ans); 48 } 49 return 0; 50 }