02_target_number.py (week 07)

김창희/7주차/02_target_number.py

@@ -0,0 +1,46 @@
+# 문제 url -> https://programmers.co.kr/learn/courses/30/lessons/43165
+class Tree:
+    def __init__(self, target_number):
+        self.tree_body = [0]
+        self.target_number = target_number
+        self.count = 1    # 이진 트리 만들때 사용
+
+    # 이진 트리 만들기    
+    def make_tree(self, numbers):
+        for number in numbers:
+            for i in range(0, self.count):
+                self.tree_body.append(number)
+                self.tree_body.append(-number)
+
+            self.count = self.count * 2
+
+    # dfs 탐색
+    def dfs(self, now_index, now_sum):
+        now_sum = now_sum + self.tree_body[now_index]
+
+        left_index = 2 * now_index + 1
+        right_index = 2 * now_index + 2
+
+        # now_index가 리프노드
+        # 모든 노드의 자식이 0 또는 2이므로, left만 검사해도 됨
+        if len(self.tree_body) - 1 < left_index:
+            if now_sum == self.target_number:
+                return 1
+            else:
+                return 0
+
+
+        left = self.dfs(left_index, now_sum)
+        right = self.dfs(right_index, now_sum)
+
+        return left + right
+
+
+
+def solution(numbers, target):
+    tree = Tree(target)
+    tree.make_tree(numbers)
+
+    answer = tree.dfs(0, 0)
+
+    return answer