POJ 1151Atlantis 扫描线+线段树求矩形面积并

题目链接

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <stack>
#include <bitset>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, n, a) for(int i = a; i<n; i++)
#define fi first
#define se second
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 500;
struct segment
{
    double l, r, h;
    int flag;
    segment(){}
    segment(double l, double r, double h, int flag):l(l), r(r), h(h), flag(flag){}
    bool operator < (segment a) const
    {
        return h<a.h;
    }
}line[maxn];
double a[maxn], sum[maxn<<2];
int cover[maxn<<2];
void pushUp(int rt, int l, int r) {
    if(cover[rt]) {
        sum[rt] = a[r+1]-a[l];
    } else if(l == r) {
        sum[rt] = 0;
    } else {
        sum[rt] = sum[rt<<1]+sum[rt<<1|1];
    }
}
void update(int L, int R, int l, int r, int rt, int flag) {
    if(L<=l&&R>=r) {
        cover[rt] += flag;
        pushUp(rt, l-1, r-1);
        return ;
    }
    int m = l+r>>1;
    if(L<=m)
        update(L, R, lson, flag);
    if(R>m)
        update(L, R, rson, flag);
    pushUp(rt, l-1, r-1);
}
int main()
{
    int n, cnt, k = 1;
    double x1, y1, x2, y2;
    while(scanf("%d", &n)&&n) {
        cnt = 0;
        mem(cover);
        for(int i = 0; i<n; i++) {
            scanf("%lf%lf%lf%lf", &x1, &y1, &x2, &y2);
            line[cnt] = segment(x1, x2, y1, 1);
            a[cnt++] = x1;
            line[cnt] = segment(x1, x2, y2, -1);
            a[cnt++] = x2;
        }
        sort(a, a+cnt);
        sort(line, line+cnt);
        double ans = 0;
        int num = unique(a, a+cnt)-a;
        for(int i = 0; i<cnt; i++) {
            int L = lower_bound(a, a+num, line[i].l)-a+1;
            int R = lower_bound(a, a+num, line[i].r)-a;
            update(L, R, 1, num, 1, line[i].flag);
            ans += sum[1]*(line[i+1].h-line[i].h);
        }
        printf("Test case #%d
", k++);
        printf("Total explored area: %.2f

", ans);
    }
    return 0;
}