Picture POJ - 1177

  1 #include <iostream>
  2 #include <algorithm>
  3 using namespace std;
  4 const int inf = 0x3f3f3f3f;
  5 const int maxn = 2e4 + 10;
  6 struct edge
  7 {
  8     int l, r;
  9     int h;
 10     int pos;
 11     bool operator < (const edge& a)const
 12     {
 13         return h < a.h;
 14     }
 15     edge(int a = 0, int b = 0, int c = 0, int d = 0) : l(a), r(b), h(c), pos(d){}
 16 }e[5010 << 1];
 17 
 18 struct node
 19 {
 20     int l, r;
 21     int flag;
 22     int len;
 23     int num;
 24     int ll, rr;
 25 }t[maxn << 2];
 26 
 27 bool cmp(edge &a, edge &b)
 28 {
 29     return a < b;
 30 }
 31 
 32 void pushup(int tar)
 33 {
 34     if (t[tar].flag)
 35     {
 36         t[tar].len = t[tar].r - t[tar].l + 1;
 37         t[tar].ll = t[tar].rr = 1;
 38         t[tar].num = 1;
 39     }
 40     else if (t[tar].l == t[tar].r)
 41         t[tar].len = t[tar].ll = t[tar].rr = t[tar].num = 0;
 42     else
 43     {
 44         t[tar].len = t[tar << 1].len + t[tar << 1 | 1].len;
 45         t[tar].num = t[tar << 1].num + t[tar << 1 | 1].num - (t[tar << 1].rr & t[tar << 1 | 1].ll);
 46         t[tar].ll = t[tar << 1].ll, t[tar].rr = t[tar << 1 | 1].rr;
 47     }
 48 }
 49 
 50 void build(int l, int r, int tar)
 51 {
 52     t[tar].l = l, t[tar].r = r, t[tar].flag = 0;
 53     t[tar].len = t[tar].num = 0;
 54     t[tar].rr = t[tar].ll = 0;
 55     if (l == r) return;
 56     int mid = (l + r) >> 1;
 57     build(l, mid, tar << 1);
 58     build(mid + 1, r, tar << 1 | 1);
 59 }
 60 
 61 void update(int l, int r, int tar, int v)
 62 {
 63     if (l == t[tar].l && r == t[tar].r)
 64     {
 65         t[tar].flag += v;
 66         pushup(tar);
 67         return;
 68     }
 69     int mid = (t[tar].l + t[tar].r) >> 1;
 70     if (r <= mid) update(l, r, tar << 1, v);
 71     else if (l > mid) update(l, r, tar << 1 | 1, v);
 72     else update(l, mid, tar << 1, v), update(mid + 1, r, tar << 1 | 1, v);
 73     pushup(tar);
 74 }
 75 
 76 int main()
 77 {
 78     int n; cin >> n;
 79     int tot = 0;
 80     int x1, y1, x2, y2;
 81     int max1, max2;
 82 
 83     max1 = inf, max2 = -inf;
 84     for (int i = 1; i <= n; i++)
 85     {
 86         scanf("%d%d%d%d", &x1, &y1, &x2, &y2);
 87         max1 = min(max1, min(x1, x2));
 88         max2 = max(max2, max(x1, x2));
 89         e[++tot] = edge(x1, x2, y1, -1);
 90         e[++tot] = edge(x1, x2, y2, 1);
 91     }
 92     sort(e + 1, e + 1 + tot, cmp);
 93     build(max1, max2 - 1, 1);
 94 
 95     int res = 0;
 96     int last = 0;
 97 
 98     for (int i = 1; i <= tot; i++)
 99     {
100         update(e[i].l, e[i].r - 1, 1, e[i].pos);
101         res += abs(t[1].len - last);
102         res += (e[i + 1].h - e[i].h) * 2 * t[1].num;
103         last = t[1].len;
104     }
105     cout << res << endl;
106 }