# 挑战程序竞赛系列（88）：3.6平面扫描（2）

## 挑战程序竞赛系列（88）：3.6平面扫描（2）

```import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Main{

String INPUT = "./data/judge/201709/P3168.txt";

public static void main(String[] args) throws IOException {
new Main().run();
}

static final int MAX_N = 25000 + 16;

class Point implements Comparable<Point>{
int ord;         // 当前轴坐标
int pos;         // 另一轴上的坐标
int id;          // 对应的矩阵id
int type;        // 起点: 0 终点: 1

Point(int ord, int pos, int id, int type){
this.ord  = ord;
this.pos  = pos;
this.id   = id;
this.type = type;
}

@Override
public int compareTo(Point that) {
if (this.ord != that.ord) {
return this.ord - that.ord;
}
if (this.pos != that.pos) {
return this.pos - that.pos;
}
return this.type - that.type;
}
}

int N;
Point[] toX = new Point[4 * MAX_N];     // 以x轴方向扫描
Point[] toY = new Point[4 * MAX_N];     // 以y轴方向扫描
boolean[] ok = new boolean[MAX_N];

void scan(Point[] ps) {

for (int i = 0; i < 4 * N; ++i) {

int j = i;
while (j < 4 * N && ps[j].ord == ps[i].ord) j++;

boolean invalid = false;
int share = 0;

for (int k = i; k < j; ++k) {
Point p = ps[k];
if (invalid) {
ok[p.id] = false;
}
if (p.type == 0) {
share ++;
if (share >= 2) {
invalid = true;
}
}
else {
share --;
if (share == 0) {
invalid = false;
}
}
}
i = j - 1;
}
}

void solve() {

Arrays.sort(toX, 0, 4 * N);
Arrays.sort(toY, 0, 4 * N);

Arrays.fill(ok, true);

scan(toX);
scan(toY);

int ans = 0;
for (int i = 0; i < N; ++i) {
if (ok[i]) ans ++;
}

out.println(ans);
}

N = ni();
for (int i = 0; i < N; ++i) {
int A = ni(), B = ni(), C = ni(), D = ni();
toX[4 * i]     = new Point(A, B, i, 0);
toX[4 * i + 1] = new Point(A, D, i, 1);
toX[4 * i + 2] = new Point(C, B, i, 0);
toX[4 * i + 3] = new Point(C, D, i, 1);

toY[4 * i]     = new Point(B, A, i, 0);
toY[4 * i + 1] = new Point(B, C, i, 1);
toY[4 * i + 2] = new Point(D, A, i, 0);
toY[4 * i + 3] = new Point(D, C, i, 1);
}

solve();
}

FastScanner in;
PrintWriter out;

void run() throws IOException {
boolean oj;
try {
oj = ! System.getProperty("user.dir").equals("F:\\java_workspace\\leetcode");
} catch (Exception e) {
oj = System.getProperty("ONLINE_JUDGE") != null;
}

InputStream is = oj ? System.in : new FileInputStream(new File(INPUT));
in = new FastScanner(is);
out = new PrintWriter(System.out);
long s = System.currentTimeMillis();
out.flush();
if (!oj){
System.out.println("[" + (System.currentTimeMillis() - s) + "ms]");
}
}

public boolean more(){
return in.hasNext();
}

public int ni(){
return in.nextInt();
}

public long nl(){
return in.nextLong();
}

public double nd(){
return in.nextDouble();
}

public String ns(){
return in.nextString();
}

public char nc(){
return in.nextChar();
}

class FastScanner {
StringTokenizer st;
boolean hasNext;

public FastScanner(InputStream is) throws IOException {
hasNext = true;
}

public String nextToken() {
while (st == null || !st.hasMoreTokens()) {
try {
} catch (Exception e) {
hasNext = false;
return "##";
}
}
return st.nextToken();
}

String next = null;
public boolean hasNext(){
next = nextToken();
return hasNext;
}

public int nextInt() {
if (next == null){
hasNext();
}
String more = next;
next = null;
return Integer.parseInt(more);
}

public long nextLong() {
if (next == null){
hasNext();
}
String more = next;
next = null;
return Long.parseLong(more);
}

public double nextDouble() {
if (next == null){
hasNext();
}
String more = next;
next = null;
return Double.parseDouble(more);
}

public String nextString(){
if (next == null){
hasNext();
}
String more = next;
next = null;
return more;
}

public char nextChar(){
if (next == null){
hasNext();
}
String more = next;
next = null;
return more.charAt(0);
}
}
}```

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