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CoastLength.java
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CoastLength.java
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// link: https://open.kattis.com/problems/coast
// name: Coast Length
package kattis;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.List;
import java.util.Queue;
import java.util.StringTokenizer;
public class CoastLength {
public static void main(String[] args) {
Kattio io = new Kattio(System.in, System.out);
int n = io.getInt();
int m = io.getInt();
boolean[][] field = new boolean[n][m];
for (int i = 0; i < n; i++) {
String word = io.getWord();
for (int j = 0; j < word.length(); j++) {
if (word.charAt(j) == '1') {
field[i][j] = true;
}
}
}
boolean[][] visited = new boolean[n][m];
Pair[] moves = { new Pair(-1, 0), new Pair(1, 0), new Pair(0, -1), new Pair(0, 1) };
int result = 0;
Queue<Pair> q = new ArrayDeque<>();
List<Pair> starting = generateStarters(n, m);
for (Pair start : starting) {
if (!visited[start.x][start.y] || field[start.x][start.y]) {
q.add(start);
visited[start.x][start.y] = true;
}
while (!q.isEmpty()) {
Pair currentPosition = q.poll();
if (field[currentPosition.x][currentPosition.y]) {
// edge land
result += 1;
continue;
}
assert (!field[currentPosition.x][currentPosition.y]);
for (Pair move : moves) {
int newX = currentPosition.x + move.x;
int newY = currentPosition.y + move.y;
if (newX < 0 || newX >= n) {
continue;
}
if (newY < 0 || newY >= m) {
continue;
}
if (field[newX][newY]) {
result += 1;
continue;
}
if (!visited[newX][newY]) {
q.add(new Pair(newX, newY));
visited[newX][newY] = true;
}
}
}
}
io.print(result);
io.close();
}
private static List<Pair> generateStarters(int n, int m) {
List<Pair> result = new ArrayList<>();
for (int i = 0; i < m; i++) {
result.add(new Pair(0, i));
result.add(new Pair(n - 1, i));
}
for (int i = 0; i < n; i++) {
result.add(new Pair(i, 0));
result.add(new Pair(i, m - 1));
}
return result;
}
static class Pair {
int x;
int y;
public Pair(int x, int y) {
super();
this.x = x;
this.y = y;
}
}
static class Kattio extends PrintWriter {
public Kattio(InputStream i) {
super(new BufferedOutputStream(System.out));
r = new BufferedReader(new InputStreamReader(i));
}
public Kattio(InputStream i, OutputStream o) {
super(new BufferedOutputStream(o));
r = new BufferedReader(new InputStreamReader(i));
}
public boolean hasMoreTokens() {
return peekToken() != null;
}
public int getInt() {
return Integer.parseInt(nextToken());
}
public double getDouble() {
return Double.parseDouble(nextToken());
}
public long getLong() {
return Long.parseLong(nextToken());
}
public String getWord() {
return nextToken();
}
private BufferedReader r;
private String line;
private StringTokenizer st;
private String token;
private String peekToken() {
if (token == null)
try {
while (st == null || !st.hasMoreTokens()) {
line = r.readLine();
if (line == null)
return null;
st = new StringTokenizer(line);
}
token = st.nextToken();
} catch (IOException e) {}
return token;
}
private String nextToken() {
String ans = peekToken();
token = null;
return ans;
}
}
}