Picture POJ - 1177 （扫描线）

扫描线求周长，可以看成两条线，一条扫x轴，一条扫y轴，然后这两天线扫过去的 周长加起来，就是周长了

#include<map>
#include<set>
#include<ctime>
#include<cmath>
#include<stack>
#include<queue>
#include<string>
#include<vector>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define first fi
#define second se
#define lowbit(x) (x & (-x))

typedef unsigned long long int ull;
typedef long long int ll;
const double pi = 4.0*atan(1.0);
const int inf = 0x3f3f3f3f;
const int maxn = ;
const int maxm = ;
using namespace std;

int n, m, tol, T;
struct Node {
    int l, r, h, f;
    bool operator < (Node a) const {
        return h < a.h;
    }
};
Node node[][maxn];
int sum[maxn << ];
int cnt[maxn << ];
int a[][maxn];

void init() {
    memset(node, , sizeof node);
    memset(a, , sizeof a);
}

void pushup(int left, int right, int flag, int root) {
    if(cnt[root]) {
        sum[root] = a[flag][right+] - a[flag][left];
    } else if(left == right) {
        sum[root] = ;
    } else {
        sum[root] = sum[root << ] + sum[root <<  | ];
    }
}

void update(int left, int right, int prel, int prer, int flag, int val, int root) {
    if(prel <= left && right <= prer) {
        cnt[root] += val;
        pushup(left, right, flag, root);
        return ;
    }
    int mid = (left + right) >> ;
    if(prel <= mid)    update(left, mid, prel, prer, flag, val, root << );
    if(prer > mid)    update(mid+, right, prel, prer, flag, val, root <<  | );
    pushup(left, right, flag, root);
}

int main() {
    while(~scanf("%d", &n)) {
        init();
        for(int i=; i<=n; i++) {
            int x1, y1, x2, y2;
            scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
            node[][i].l = x1, node[][i+n].l = x1;
            node[][i].r = x2, node[][i+n].r = x2;
            node[][i].h = y1, node[][i+n].h = y2;
            node[][i].f = ,  node[][i+n].f = -;
            a[][i] = x1, a[][i+n] = x2;
            node[][i].l = y1, node[][i+n].l = y1;
            node[][i].r = y2, node[][i+n].r = y2;
            node[][i].h = x1, node[][i+n].h = x2;
            node[][i].f = ,  node[][i+n].f = -;
            a[][i] = y1, a[][i+n] = y2;
        }
        n <<= ;
        sort(node[]+, node[]++n);
        sort(node[]+, node[]++n);
        sort(a[]+, a[]+n+);
        sort(a[]+, a[]+n+);
        int cnt1 = unique(a[]+, a[]++n) - (a[]+);
        int cnt2 = unique(a[]+, a[]++n) - (a[]+);
        int ans = ;
        int last = ;
        memset(sum, , sizeof sum);
        memset(cnt, , sizeof cnt);
        for(int i=; i<=n; i++) {
            int l = lower_bound(a[]+, a[]+cnt1+, node[][i].l) - a[];
            int r = lower_bound(a[]+, a[]+cnt1+, node[][i].r) - a[];
            update(, cnt1, l, r-, , node[][i].f, );
            ans += abs(sum[] - last);
            last = sum[];
        }
        last = ;
        memset(sum, , sizeof sum);
        memset(cnt, , sizeof cnt);
        for(int i=; i<=n; i++) {
            int l = lower_bound(a[]+, a[]+cnt2+, node[][i].l) - a[];
            int r = lower_bound(a[]+, a[]+cnt2+, node[][i].r) - a[];
            update(, cnt2, l, r-, , node[][i].f, );
            ans += abs(sum[] - last);
            last = sum[];
        }
        printf("%d\n", ans);
    }
    return ;
}