From f1efb560ebc1657243669ba073db28314b4d9564 Mon Sep 17 00:00:00 2001
From: koishi-dream <106549056+koishi-daisuki@users.noreply.github.com>
Date: Mon, 30 Sep 2024 18:46:55 -0400
Subject: [PATCH] Add Depth First Search in Java (#3842)

---
 archive/j/java/DepthFirstSearch.java | 92 ++++++++++++++++++++++++++++
 archive/j/java/testinfo.yml          |  2 +-
 2 files changed, 93 insertions(+), 1 deletion(-)
 create mode 100644 archive/j/java/DepthFirstSearch.java

diff --git a/archive/j/java/DepthFirstSearch.java b/archive/j/java/DepthFirstSearch.java
new file mode 100644
index 000000000..835166438
--- /dev/null
+++ b/archive/j/java/DepthFirstSearch.java
@@ -0,0 +1,92 @@
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Stream;
+
+public class DepthFirstSearch {
+
+    public static void main(String[] args) {
+        if (args.length != 3 || args[0].isEmpty() || args[1].isEmpty() || args[2].isEmpty()) {
+            handleError();
+            return;
+        }
+        int matrixSize = args[0].split(",").length;
+        if (matrixSize != Math.pow(args[1].split(",").length, 2)){
+            handleError();
+            return;
+        }
+        List<Integer> vertices = Stream.of(args[1].split(","))
+                .map(String::trim)
+                .map(Integer::parseInt)
+                .toList();
+        int[][] matrix = new int[matrixSize][matrixSize];
+        int count = 0;
+        for (int i = 0; i < vertices.size(); i++) {
+            for (int j = 0; j < vertices.size(); j++) {
+                matrix[i][j] = Integer.parseInt(args[0].split(",")[count].trim());
+                count++;
+            }
+        }
+        DFSGraph dfsGraph = new DFSGraph(matrix, vertices);
+        int search = Integer.parseInt(args[2]);
+        System.out.println(dfsGraph.depthFirstSearch(0, 0, search));
+
+    }
+
+    private static void handleError() {
+        System.out.println("Usage: please provide a tree in an adjacency matrix form " +
+                "(\"0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, " +
+                "0\") together with a list of vertex values (\"1, 3, 5, 2, 4\") " +
+                "and the integer to find (\"4\")");
+    }
+
+    public static class DFSGraph {
+
+        int[][] matrix;
+        List<Integer> vertices;
+        List<Integer> visited;
+
+        public DFSGraph(int[][] matrix, List<Integer> vertices) {
+            this.matrix = matrix;
+            this.vertices = vertices;
+            this.visited = new ArrayList<>(vertices.size());
+        }
+
+        public int getNextNodeIndex(int row, int current_column) {
+            for (int i = current_column; i < vertices.size(); i++) {
+                if (!visited.contains(vertices.get(i)) && matrix[row][i] == 1) {
+                    return i;
+                }
+            }
+            return -1;
+        }
+
+        public boolean depthFirstSearch(int row, int column, int search) {
+            // if the current node is the search node, return true
+            boolean found = this.vertices.get(row) == search;
+            if (found) {
+                return true;
+            }
+            // if the current node is the first search node, that is not a valid connection,
+            // get the next node of the current row
+            if (matrix[row][column] == 0) {
+                int nextNodeIndex = getNextNodeIndex(row, column);
+                if (nextNodeIndex == -1) {
+                    return false;
+                } else {
+                    column = nextNodeIndex;
+                }
+            }
+            // mark the current node as visited
+            visited.add(vertices.get(row));
+            while (getNextNodeIndex(row, column) != -1) {
+                boolean f = depthFirstSearch(getNextNodeIndex(row, column), row, search);
+                if (f) {
+                    return true;
+                }
+                column++;
+            }
+            return false;
+        }
+
+    }
+}
diff --git a/archive/j/java/testinfo.yml b/archive/j/java/testinfo.yml
index 98376eb10..2d3ee7d28 100644
--- a/archive/j/java/testinfo.yml
+++ b/archive/j/java/testinfo.yml
@@ -4,6 +4,6 @@ folder:
 
 container:
   image: "openjdk"
-  tag: "11-slim" 
+  tag: "23-slim"
   build: "javac {{ source.name}}{{ source.extension }}"
   cmd: "java {{ source.name }}"