【线段树+扫描线】 HDOJ 1828 && POJ 1177 Picture

线段树+扫描线+离散化求周长。求周长和求面积其实差不多。。。就改一下pushup，考虑一下合并的段数（用来计算另一维）。。。

#include <iostream>#include <sstream>#include <algorithm>#include <vector>#include <queue>#include <stack>#include <map>#include <set>#include <bitset>#include <cstdio>#include <cstring>#include <cstdlib>#include <cmath>#include <climits>#define maxn 5005#define eps 1e-6#define mod 200000007#define INF 99999999#define lowbit(x) (x&(-x))#define lson o<<1, L, mid#define rson o<<1 | 1, mid+1, Rtypedef long long LL;using namespace std;int cover[maxn<<3];int once[maxn<<3];int segnum[maxn<<3];int lc[maxn<<3], rc[maxn<<3];struct node{int x1, x2;int h, flag;}line[maxn<<2];int x[maxn<<2];int m, xcnt, n;int ql, qr, k;void init(void){memset(segnum, 0, sizeof segnum);memset(cover, 0, sizeof cover);memset(once, 0, sizeof once);memset(lc, 0, sizeof lc);memset(rc, 0, sizeof rc);}int cmp1(int a, int b){return a<b;}int cmp2(node a, node b){return a.h<b.h;}int search(int tmp){int bot=1, top=xcnt, mid;while(top>=bot){mid=(top+bot)>>1;if(x[mid]==tmp) break;if(x[mid]>tmp) top=mid-1;else bot=mid+1;}return mid;}void read(void){int i, j;for(i=0, j=0;i<n;i++){scanf("%d%d%d%d", &line[j].x1, &line[j].h, &line[j+1].x2, &line[j+1].h);line[j].x2=line[j+1].x2, line[j+1].x1=line[j].x1;line[j].flag=1, line[j+1].flag=-1;x[j+1]=line[j].x1, x[j+2]=line[j+1].x2, j+=2;}m=j, xcnt=j;}void work(void){sort(x+1, x+xcnt+1, cmp1);sort(line, line+m, cmp2);int i, j;for(i=2, j=2;i<=xcnt;i++)if(x[i]!=x[i-1])x[j++]=x[i];xcnt=j-1;}void pushup(int o, int L, int R){if(cover[o]>0){segnum[o]=1;lc[o]=rc[o]=1;once[o]=x[R+1]-x[L];}else{if(L==R){once[o]=0;segnum[o]=0;lc[o]=rc[o]=0;}else{once[o]=once[o<<1]+once[o<<1 | 1];segnum[o]=segnum[o<<1]+segnum[o<<1 | 1];if(rc[o<<1] && lc[o<<1 | 1]) segnum[o]--;lc[o]=lc[o<<1];rc[o]=rc[o<<1 | 1];}}}void updata(int o, int L, int R){if(ql<=L && qr>=R){cover[o]+=k;pushup(o, L, R);return;}int mid=(R+L)>>1;if(ql<=mid) updata(lson);if(qr>mid) updata(rson);pushup(o, L, R);}void solve(void){int res=0, i, tmp=0;for(i=0;i<m;i++){ql=search(line[i].x1);qr=search(line[i].x2)-1;k=line[i].flag;updata(1, 1, xcnt-1);res+=abs(once[1]-tmp);tmp=once[1];res+=segnum[1]*2*(line[i+1].h-line[i].h);}printf("%d\n", res);}int main(void){while(scanf("%d",&n)!=EOF){init();read();work();solve();}return 0;}