USACO5.5 矩形周长 Picture | 扫描线 + 线段树

  1 #include <cstdio>
  2 #include <string>
  3 #include <cstring>
  4 #include <algorithm>
  5 
  6 int read(); int abs(int);
  7 
  8 struct Rectangle {
  9     int x1, x2, y1, y2;
 10 } rec[5005];
 11 
 12 struct Line {
 13     int l, r, h, f;
 14     bool operator < (const Line &cmp) const {
 15         if (h == cmp.h) return f > cmp.f;
 16         return h < cmp.h;
 17     }
 18 } line[10005];
 19 
 20 int hash[10005], cnt, sum[40005], tag[40005];
 21 
 22 int find(int x, int l, int r) {
 23     while (l <= r) {
 24         int mid = l + ((r - l) >> 1);
 25         if (hash[mid] < x) l = mid + 1;
 26         else if (hash[mid] == x) return mid;
 27         else r = mid - 1;
 28     }
 29 }
 30 
 31 void maintain(int cur, int l, int r) {
 32     if (tag[cur]) sum[cur] = hash[r + 1] - hash[l];
 33     else if (l == r) sum[cur] = 0;
 34     else sum[cur] = sum[cur << 1] + sum[cur << 1 | 1];
 35 }
 36 
 37 void update(int cur, int l, int r, int L, int R, int flag) {
 38     if (L <= l && r <= R) tag[cur] += flag;
 39     else {
 40         int mid = l + ((r - l) >> 1);
 41         if (L <= mid) update(cur << 1, l, mid, L, R, flag);
 42         if (mid < R) update(cur << 1 | 1, mid + 1, r, L, R, flag);
 43     }
 44     maintain(cur, l, r);
 45 }
 46 
 47 int solve() {
 48     int res = 0;
 49     std::sort(hash + 1, hash + cnt + 1);
 50     std::sort(line + 1, line + cnt + 1);
 51     for (int i = 1; i <= cnt; ++ i) {
 52         int l = find(line[i].l, 1, cnt),
 53             r = find(line[i].r, 1, cnt) - 1;
 54         if (l <= r) {
 55             int tmp = sum[1];
 56             update(1, 1, cnt, l, r, line[i].f);
 57             res += abs(sum[1] - tmp);
 58         }
 59     }
 60     return res;
 61 }
 62 
 63 int main() {
 64     int n = read(), ans = 0;
 65     for (int i = 1; i <= n; ++ i) {
 66         rec[i].x1 = read(), rec[i].y1 = read(),
 67         rec[i].x2 = read(), rec[i].y2 = read();
 68         hash[++cnt] = rec[i].x1, line[cnt].l = rec[i].x1,
 69         line[cnt].r = rec[i].x2, line[cnt].h = rec[i].y1, line[cnt].f = 1;
 70         hash[++cnt] = rec[i].x2, line[cnt].l = rec[i].x1,
 71         line[cnt].r = rec[i].x2, line[cnt].h = rec[i].y2, line[cnt].f = -1;
 72     }
 73     ans += solve();
 74     cnt = 0;
 75     for (int i = 1; i <= n; ++ i) {
 76         hash[++cnt] = rec[i].y1, line[cnt].l = rec[i].y1,
 77         line[cnt].r = rec[i].y2, line[cnt].h = rec[i].x1, line[cnt].f = 1;
 78         hash[++cnt] = rec[i].y2, line[cnt].l = rec[i].y1,
 79         line[cnt].r = rec[i].y2, line[cnt].h = rec[i].x2, line[cnt].f = -1;
 80     }
 81     ans += solve();
 82     printf("%d\n", ans);
 83     return 0;
 84 }
 85 
 86 int abs(int x) {
 87     if (x >= 0) return x; return -x;
 88 }
 89 
 90 int read() {
 91     int x = 0, f = 1;
 92     char c = getchar();
 93     while (!isdigit(c)) {
 94         if (c == ‘-‘) f = -1;
 95         c = getchar();
 96     }
 97     while (isdigit(c)) {
 98         x = (x << 3) + (x << 1) + (c ^ 48);
 99         c = getchar();
100     }
101     return x * f;
102 }