POJ1151(线段树+扫描线求矩形面积并)
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POJ1151(线段树+扫描线求矩形面积并)
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題目：http://poj.org/problem?id=1151
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#include <iostream> #include <string.h> #include <algorithm> #include <stdio.h>using namespace std; const int N = 10005;struct node {int l,r;int cov;double len; };struct line {double x;double y1;double y2;int f;bool operator < (const line &a) const{return x < a.x;} };class SegTree {private:node tree[N];double num[N];int ncount;public:SegTree(double a[],int n){for(int i=0;i<n;i++)num[i] = a[i];ncount = n;Build(0,n-1,1);}void Build(int l,int r,int rt){tree[rt].l = l;tree[rt].r = r;tree[rt].cov = 0;tree[rt].len = 0;if(l+1 == r) return;int mid = (l+r)>>1;Build(l,mid,2*rt);Build(mid,r,2*rt+1);}void Insert(int l,int r,int p){if(tree[p].l == l && tree[p].r == r){tree[p].cov++;tree[p].len = num[r] - num[l];return;}int mid = (tree[p].l + tree[p].r)>>1;if(r <= mid)Insert(l,r,2*p);else if(l >= mid)Insert(l,r,2*p+1);else{Insert(l,mid,2*p);Insert(mid,r,2*p+1);}if(tree[p].cov == 0)tree[p].len = tree[2*p].len + tree[2*p+1].len;}void Delete(int l,int r,int p){if(tree[p].l == l && tree[p].r == r){tree[p].cov--;if(tree[p].cov <= 0){if(tree[p].l+1 < tree[p].r)tree[p].len = tree[2*p].len + tree[2*p+1].len;elsetree[p].len = 0;}return;}int mid = (tree[p].l + tree[p].r)>>1;if(r <= mid)Delete(l,r,2*p);else if(l >= mid)Delete(l,r,2*p+1);else{Delete(l,mid,2*p);Delete(mid,r,2*p+1);}if(tree[p].cov == 0)tree[p].len = tree[2*p].len + tree[2*p+1].len;}double getLen(){return tree[1].len;} };int main() {int test=0,n;double x1,y1,x2,y2;double yval[N];line data[N];while(~scanf("%d",&n)){if(n==0) break;test++;int l1 = 0;int l2 = 0;for(int i=0;i<n;i++){scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);yval[l1++] = y1;yval[l1++] = y2;data[l2].x = x1;data[l2].y1 = y1;data[l2].y2 = y2;data[l2].f = -1;l2++;data[l2].x = x2;data[l2].y1 = y1;data[l2].y2 = y2;data[l2].f = 1;l2++;}sort(yval,yval+l1);sort(data,data+l2);l1 = unique(yval,yval+l1) - yval;double sum = 0;SegTree stree(yval,l1);for(int i=0;i<l2-1;i++){int l,r;l = lower_bound(yval,yval+l1,data[i].y1) - yval;r = lower_bound(yval,yval+l1,data[i].y2) - yval;if(data[i].f == -1)stree.Insert(l,r,1);elsestree.Delete(l,r,1);sum += stree.getLen() * (data[i+1].x - data[i].x);}printf("Test case #%d\n", test);printf("Total explored area: ");printf("%.2lf\n\n", sum);}return 0; }
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