HDU 1828 Picture (rectangle perimeter and), hdu1828

HDU 1828 Picture (rectangle perimeter and), hdu1828
HDU 1828 Picture

Question Link

Given n rectangles, the perimeter of the rectangle is output and

Idea: Use the line segment tree for maintenance, scanning from four directions each time. When there are multiple sections, the length of the Section not covered is queried, and the length of the circumference is added, the answer is added to all four directions.

Code:

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int N = 5005;int n;struct Rec {int x1, y1, x2, y2;void read() {scanf("%d%d%d%d", &x1, &y1, &x2, &y2);x1 += 10000; y1 += 10000; x2 += 10000; y2 += 10000;}} rec[N];struct Line {int l, r, y, flag;Line() {}Line(int l, int r, int y, int flag) {this->l = l; this->r = r;this->y = y; this->flag = flag;}} line[N * 2];bool cmp1(Line a, Line b) {if (a.y == b.y) return a.flag > b.flag;return a.y < b.y;}bool cmp2(Line a, Line b) {if (a.y == b.y) return a.flag > b.flag;return a.y > b.y;}#define lson(x) ((x<<1)+1)#define rson(x) ((x<<1)+2)struct Node {int l, r, add, addv, num;bool cover;void init(int l, int r) {this->l = l; this->r = r;add = addv = num = 0;cover = false;}void gao(int v) {addv += v;if (add == 0) num = r - l + 1;add += v;if (add == 0) num = 0;}} node[4 * 20005];void pushup(int x) {if (node[lson(x)].cover && node[rson(x)].cover && node[lson(x)].add == node[rson(x)].add) {node[x].cover = true;node[x].add = node[lson(x)].add;} else node[x].cover = false;node[x].num = node[lson(x)].num + node[rson(x)].num;}void pushdown(int x) {if (node[x].addv) {node[lson(x)].gao(node[x].addv);node[rson(x)].gao(node[x].addv);node[x].addv = 0;}}void build(int l, int r, int x = 0) {node[x].init(l, r);if (l == r) {node[x].cover = true;return;}int mid = (l + r) / 2;build(l, mid, lson(x));build(mid + 1, r, rson(x));pushup(x);}void add(int l, int r, int v, int x = 0) {if (node[x].cover && node[x].l >= l && node[x].r <= r) {node[x].gao(v);return;}int mid = (node[x].l + node[x].r) / 2;pushdown(x);if (l <= mid) add(l, r, v, lson(x));if (r > mid) add(l, r, v, rson(x));pushup(x);}int query(int l, int r, int x = 0) {if (node[x].cover && node[x].l >= l && node[x].r <= r)return node[x].num;int mid = (node[x].l + node[x].r) / 2;pushdown(x);int ans = 0;if (l <= mid) ans += query(l, r, lson(x));if (r > mid) ans += query(l, r, rson(x));pushup(x);return ans;}int solve() {build(0, 20000);int ans = 0;for (int i = 0; i < 2 * n; i++) {if (line[i].flag)ans += line[i].r - line[i].l - query(line[i].l, line[i].r - 1);add(line[i].l, line[i].r - 1, line[i].flag);}return ans;}int gao() {int ans = 0;for (int i = 0; i < n; i++) {line[i * 2] = Line(rec[i].x1, rec[i].x2, rec[i].y1, 1);line[i * 2 + 1] = Line(rec[i].x1, rec[i].x2, rec[i].y2, -1);}sort(line, line + 2 * n, cmp1);ans += solve();for (int i = 0; i < n; i++) {line[i * 2] = Line(rec[i].x1, rec[i].x2, rec[i].y2, 1);line[i * 2 + 1] = Line(rec[i].x1, rec[i].x2, rec[i].y1, -1);}sort(line, line + 2 * n, cmp2);ans += solve();return ans;}int main() {while (~scanf("%d", &n)) {for (int i = 0; i < n; i++)rec[i].read();int ans = 0;ans += gao();for (int i = 0; i < n; i++) {swap(rec[i].x1, rec[i].y1);swap(rec[i].x2, rec[i].y2);}ans += gao();printf("%d\n", ans);}return 0;}

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