【Arai60】52問目 39. Combination Sum

arai60/50-53_Greedy_Backtracking/52_39_Combination Sum/level_1.py

@@ -0,0 +1,17 @@
+# Backtracking
+class Solution:
+    def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
+        def make_combination(remain, current, begin):
+            if remain == 0:
+                combinations.append(current[:])
+                return
+            if remain < 0:
+                return
+            for i in range(begin, len(candidates)):
+                current.append(candidates[i])
+                make_combination(remain - candidates[i], current, i)
+                current.pop()
+
+        combinations = []
+        make_combination(target, [], 0)
+        return combinations

arai60/50-53_Greedy_Backtracking/52_39_Combination Sum/level_2.py

@@ -0,0 +1,17 @@
+# Backtracking
+# 再帰が深いので、stackで書き直した
+class Solution:
+    def combinationSum(
+        self, candidates: List[int], target: int) -> List[List[int]]:
+        stack = [(target, [], 0)]
+        combinations = []
+        while stack:
+            before_remain, before_combination, begin = stack.pop()
+            for i in range(begin, len(candidates)):
+                remain = before_remain - candidates[i]
+                combination = before_combination + [candidates[i]]
+                if remain == 0:
+                    combinations.append(combination)
+                elif 0 < remain:
+                    stack.append((remain, combination, i))
+        return combinations

arai60/50-53_Greedy_Backtracking/52_39_Combination Sum/level_3.py

@@ -0,0 +1,17 @@
+sys.setrecursionlimit(2000)
+class Solution:
+    def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
+        def make_combinations(remain, combination, begin):
+            if remain < 0:
+                return
+            if remain == 0:
+                combinations.append(combination[:])
+                return
+            for i in range(begin, len(candidates)):
+                combination.append(candidates[i])
+                make_combinations(remain - candidates[i], combination, i)
+                combination.pop()
+
+        combinations = []
+        make_combinations(target, [], 0)
+        return combinations