solve: 코딩테스트 문제 풀이 - 29일차

Author: OhChangEun

2025-09-10/오창은/프로그래머스_길찾기 게임.java

@@ -0,0 +1,75 @@
+import java.util.*;
+
+class Solution {
+   	class Node {
+        int x, y, num; 
+        Node left, right;
+        public Node (int x, int y, int num) {
+            this.x = x;
+            this.y = y;
+            this.num = num;
+        }
+    }
+    
+    List<Integer> preorderList;
+    List<Integer> postorderList;
+    public int[][] solution(int[][] nodeinfo) {
+      	int n = nodeinfo.length;
+        Node[] nodes = new Node[n];
+        
+        for (int i=0; i<n; i++) {
+            int x = nodeinfo[i][0];
+            int y = nodeinfo[i][1];
+            nodes[i] = new Node(x, y, i+1);
+        }
+        
+        Arrays.sort(nodes, (a, b) -> {
+          	if (a.y == b.y) return a.x - b.x; 
+            return b.y - a.y;
+        });
+       
+        Node root = nodes[0];
+        for (int i=1; i<n; i++) {
+            insertNode(root, nodes[i]);
+        }
+       
+        preorderList = new ArrayList<>();
+        postorderList = new ArrayList<>();
+       	preorder(root);
+       	postorder(root);
+       
+        int[][] answer = new int[2][n];
+        for (int i=0; i<n; i++) {
+            answer[0][i] = preorderList.get(i);
+            answer[1][i] = postorderList.get(i);
+        }
+        
+        return answer;
+    }
+   	private void preorder(Node node) {
+        if (node == null) return; 
+        preorderList.add(node.num);
+        preorder(node.left);
+        preorder(node.right);
+    } 
+   	private void postorder(Node node) {
+        if (node == null) return; 
+        postorder(node.left);
+        postorder(node.right);
+        postorderList.add(node.num);
+    } 
+    
+    private void insertNode(Node parent, Node child) {
+        if (child.x < parent.x) {
+            if (parent.left == null) 
+                parent.left = child;
+            else 
+                insertNode(parent.left, child);
+        } else {
+            if (parent.right == null)
+                parent.right = child; 
+            else 
+                insertNode(parent.right, child);
+        }
+    }
+}