HDOJ 1828 线段树 矩形周长并

链接：

http://acm.hdu.edu.cn/showproblem.php?pid=1828

代码：

#include <map>
#include <set>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
#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 all(x) (x).begin(),(x).end()
#define pb push_back
#define mp make_pair
#define lson l,m,rt<<1  
#define rson m+1,r,rt<<1|1 
typedef long long ll;
typedef vector<int> VI;
typedef pair<int, int> PII;
const ll MOD = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const int MAXN = 2e4 + 7;
// head

int cnt[MAXN << 2];
int sum[MAXN << 2], num[MAXN << 2];
int lbd[MAXN << 2], rbd[MAXN << 2];

struct seg {
    int l, r, h, d;
    const bool operator<(const seg &t) const {
        return h < t.h;
    }
}s[MAXN << 1];

void pushup(int l, int r, int rt) {
    if (cnt[rt]) {
        lbd[rt] = rbd[rt] = 1;
        sum[rt] = r - l + 1;
        num[rt] = 2;
    }
    else if (l == r) lbd[rt] = rbd[rt] = sum[rt] = num[rt] = 0;
    else {
        lbd[rt] = lbd[rt << 1], rbd[rt] = rbd[(rt << 1) | 1];
        sum[rt] = sum[rt << 1] + sum[(rt << 1) | 1];
        num[rt] = num[rt << 1] + num[(rt << 1) | 1];
        if (rbd[rt << 1] && lbd[(rt << 1) | 1]) num[rt] -= 2;
    }
}

void update(int L, int R, int d, int l, int r, int rt) {
    if (L <= l && r <= R) {
        cnt[rt] += d;
        pushup(l, r, rt);
        return;
    }
    int m = (l + r) >> 1;
    if (L <= m) update(L, R, d, lson);
    if (R > m) update(L, R, d, rson);
    pushup(l, r, rt);
}

int main() {
    int n;
    while (cin >> n) {
        int m = 0;
        rep(i, 0, n) {
            int x1, x2, y1, y2;
            scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
            s[m++] = seg{ x1,x2,y1,1 };
            s[m++] = seg{ x1,x2,y2,-1 };
        }
        sort(s, s + m);
        int ans = 0, last = 0;
        rep(i, 0, m) {
            if (s[i].l < s[i].r) update(s[i].l, s[i].r - 1, s[i].d, -1e4, 1e4, 1);
            ans += num[1] * (s[i + 1].h - s[i].h);
            ans += abs(sum[1] - last);
            last = sum[1];
        }
        cout << ans << endl;
    }
    return 0;
}