【HDOJ】1542 Atlantis

离散化+线段树+扫描线，求覆盖面积。

/* 1542 */
#include <iostream>
#include <string>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <deque>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <climits>
#include <cctype>
#include <cassert>
#include <functional>
#include <iterator>
#include <iomanip>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,1024000")

#define sti                set<int>
#define stpii            set<pair<int, int> >
#define mpii            map<int,int>
#define vi                vector<int>
#define pii                pair<int,int>
#define vpii            vector<pair<int,int> >
#define rep(i, a, n)     for (int i=a;i<n;++i)
#define per(i, a, n)     for (int i=n-1;i>=a;--i)
#define clr                clear
#define pb                 push_back
#define mp                 make_pair
#define fir                first
#define sec                second
#define all(x)             (x).begin(),(x).end()
#define SZ(x)             ((int)(x).size())
#define lson            l, mid, rt<<1
#define rson            mid+1, r, rt<<1|1

typedef struct segment_t {
    double l, r, h;
    int f;

    friend bool operator< (const segment_t& a, const segment_t& b) {
        return a.h < b.h;
    }

} segment_t;

typedef struct {
    int l, r, c;
    double len;
} node_t;

const int maxn = 205;
double X[maxn];
segment_t seg[maxn];
node_t nd[maxn<<2];

void build(int l, int r, int rt) {
    nd[rt].l = l;
    nd[rt].r = r;
    nd[rt].c = 0;
    nd[rt].len = 0;

    if (l == r)
        return ;

    int mid = (l + r) >> 1;
    build(lson);
    build(rson);
}

void PushUp(int rt) {
    if (nd[rt].c)
        nd[rt].len = X[nd[rt].r+1] - X[nd[rt].l];
    else if (nd[rt].r == nd[rt].l)
        nd[rt].len = 0;
    else
        nd[rt].len = nd[rt<<1].len + nd[rt<<1|1].len;
}

void update(int L, int R, int delta, int rt) {
    if (L<=nd[rt].l && nd[rt].r<=R) {
        nd[rt].c += delta;
        PushUp(rt);
        return ;
    }

    int mid = (nd[rt].l + nd[rt].r) >> 1;

    if (mid >= R) {
        update(L, R, delta, rt<<1);
    } else if (mid < L) {
        update(L, R, delta, rt<<1|1);
    } else {
        update(L, R, delta, rt<<1);
        update(L, R, delta, rt<<1|1);
    }

    PushUp(rt);
}

int main() {
    ios::sync_with_stdio(false);
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif

    int n, m, xn;
    double x1, x2, y1, y2;
    double ans;
    int L, R;
    int tt = 0;

    while (scanf("%d",&n)!=EOF && n) {
        ans = 0.;
        m = 0;
        rep(i, 0, n) {
            scanf("%lf %lf %lf %lf", &x1,&y1,&x2,&y2);
            seg[m].l = seg[m+1].l = x1;
            seg[m].r = seg[m+1].r = x2;
            seg[m].h = y1;
            seg[m].f = 1;
            seg[m+1].h = y2;
            seg[m+1].f = -1;

            X[m] = x1;
            X[m+1] = x2;

            m += 2;
        }

        sort(seg, seg+m);
        sort(X, X+m);
        xn = unique(X, X+m)-X;

        build(0, xn-1, 1);

        rep(i, 0, m) {
            L = lower_bound(X, X+xn, seg[i].l) - X;
            R = lower_bound(X, X+xn, seg[i].r) - X - 1;
            update(L, R, seg[i].f, 1);
            ans += (seg[i+1].h - seg[i].h) * nd[1].len;
            #ifndef ONLINE_JUDGE
                printf("L = %d, R = %d, len = %.2lf
", L, R, nd[1].len);
            #endif
        }

        printf("Test case #%d
", ++tt);
        printf("Total explored area: %.02lf

", ans);
    }

    #ifndef ONLINE_JUDGE
        printf("time = %d.
", (int)clock());
    #endif

    return 0;
}