[PGS]타겟 넘버

target_number.java

@@ -0,0 +1,53 @@
+import java.util.*;
+
+class Solution {
+    int answer = 0;
+    List<List<Integer>> adj = new ArrayList<>();
+    List<Integer> sumOfNode = new ArrayList<>();
+
+    public int solution(int[] numbers, int target) {
+        adj.add(new ArrayList<>());   // 0번 노드 = 루트
+        sumOfNode.add(0);
+
+        List<Integer> currentLevel = new ArrayList<>();
+        currentLevel.add(0);
+
+        for (int num : numbers) {
+            List<Integer> nextLevel = new ArrayList<>();
+            for (int parent : currentLevel) {
+                int parentSum = sumOfNode.get(parent);
+
+                for (int sign : new int[]{1, -1}) {
+                    int child = adj.size();
+                    adj.add(new ArrayList<>());
+                    sumOfNode.add(parentSum + sign * num);
+                    adj.get(parent).add(child);
+                    nextLevel.add(child);
+                }
+            }
+            currentLevel = nextLevel;
+        }
+
+        boolean[] visited = new boolean[adj.size()];
+        dfs(0, target, visited);
+
+        return answer;
+    }
+
+    public void dfs(int v, int target, boolean[] visited) {
+        visited[v] = true;
+
+        if (adj.get(v).isEmpty()) {
+            if (sumOfNode.get(v) == target) {
+                answer++;
+            }
+            return;
+        }
+
+        for (int next : adj.get(v)) {
+            if (!visited[next]) {
+                dfs(next, target, visited);
+            }
+        }
+    }
+}