40. Combination Sum II

Author: papilo-cloud

Backtracking/combination_sum_2.py

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+# Given a collection of candidate numbers (candidates) and a target number (target),
+# find all unique combinations in candidates where the candidate numbers sum to target.
+
+# Each number in candidates may only be used once in the combination.
+
+# Note: The solution set must not contain duplicate combinations.
+
+# Example 1:
+# Input: candidates = [10,1,2,7,6,1,5], target = 8
+# Output: 
+# [
+# [1,1,6],
+# [1,2,5],
+# [1,7],
+# [2,6]
+# ]
+
+# Example 2:
+# Input: candidates = [2,5,2,1,2], target = 5
+# Output: 
+# [
+# [1,2,2],
+# [5]
+# ]
+ 
+
+# Constraints:
+
+# 1 <= candidates.length <= 100
+# 1 <= candidates[i] <= 50
+# 1 <= target <= 30
+
+
+from typing import List
+class Solution:
+    def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:
+        ans = []
+        def dfs(s, t, path):
+            if t < 0:
+                return
+            if t == 0:
+                ans.append(path.copy())
+                return
+            for i in range(s, len(candidates)):
+                if i > s and candidates[i] == candidates[i - 1]:
+                    continue
+                path.append(candidates[i])
+                dfs(i + 1, t - candidates[i], path)
+                path.pop()
+        candidates.sort()
+        dfs(0, target, [])
+        return ans