From f5a35f8a888099414082cd3c2c81098acda69ea5 Mon Sep 17 00:00:00 2001
From: alastifer <grishkevichaaa@gmail.com>
Date: Tue, 3 Oct 2017 18:19:21 +0300
Subject: [PATCH] DFS algorithm in Java

---
 graph/bfs_dfs/dfs/DFS.java | 104 +++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 graph/bfs_dfs/dfs/DFS.java

diff --git a/graph/bfs_dfs/dfs/DFS.java b/graph/bfs_dfs/dfs/DFS.java
new file mode 100644
index 00000000..936d54c5
--- /dev/null
+++ b/graph/bfs_dfs/dfs/DFS.java
@@ -0,0 +1,104 @@
+/**
+ * Input file example:
+ *
+ * 8
+ * INF 1 1 INF INF INF INF INF
+ * 1 INF INF 1 1 INF INF INF
+ * 1 INF INF INF INF 1 1 INF
+ * INF 1 INF INF INF INF INF INF
+ * INF 1 INF INF INF INF INF 1
+ * INF INF 1 INF INF INF INF INF
+ * INF INF 1 INF INF INF INF INF
+ * INF INF INF INF 1 INF INF INF
+ * 1
+ *
+ * First line is number of elements in graph
+ * Next n-lines is graph
+ * Last line is begin point
+ *
+ * Output file:
+ * 1 -> 2 -> 4 -> 5 -> 8 -> 3 -> 6 -> 7
+ *
+ */
+
+package dfs;
+
+import java.io.BufferedWriter;
+import java.io.FileInputStream;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.*;
+
+public class DFS {
+
+    private static final String INPUT_FILE_PATH = "input.txt";
+
+    private static final String OUTPUT_FILE_PATH = "output.txt";
+
+    private static final int INF = Integer.MAX_VALUE / 2;
+
+    private static boolean used[];
+
+    private static int begin;
+
+    public static void main(String[] args) {
+        int[][] matrix = readMatrixFromFile();
+        used = new boolean[matrix.length];
+        String answer = dfs(matrix, begin);
+        printSolution(answer);
+    }
+
+    private static int[][] readMatrixFromFile() {
+        int[][] matrix = null;
+
+        try (Scanner scanner = new Scanner(new FileInputStream(INPUT_FILE_PATH))) {
+            int matrixSize = Integer.parseInt(scanner.nextLine());
+            matrix = new int[matrixSize][matrixSize];
+
+            for (int row = 0; row < matrixSize; row++) {
+                String[] numbers = scanner.nextLine().split(" ");
+                for (int col = 0; col < matrixSize; col++) {
+                    if (numbers[col].equals("INF")) {
+                        matrix[row][col] = INF;
+                    } else {
+                        matrix[row][col] = Integer.parseInt(numbers[col]);
+                    }
+                }
+            }
+
+            begin = scanner.nextInt() - 1;
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        return matrix;
+    }
+
+    private static String dfs(int[][] matrix, int v) {
+        StringBuilder answer = new StringBuilder();
+
+        used[v] = true;
+        answer.append(v + 1).append(" ");
+        for (int nv = 0; nv < matrix.length; nv++) {
+            if (!used[nv] && matrix[v][nv] != INF) {
+                answer.append(dfs(matrix, nv));
+            }
+        }
+
+        return answer.toString();
+    }
+
+    private static void printSolution(String answer) {
+        try (BufferedWriter writer = new BufferedWriter(new FileWriter(OUTPUT_FILE_PATH))) {
+            String[] points = answer.split(" ");
+            writer.write(points[0]);
+
+            for (int i = 1; i < points.length; i++) {
+                writer.write(" -> " + points[i]);
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+}