feat: add solutions to lc problem: No.0039

No.0039.Combination Sum

Author: yanglbme

solution/0000-0099/0039.Combination Sum/README.md

@@ -65,21 +65,19 @@ DFS。
 ```python
 class Solution:
     def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
-        ans = []
-        n = len(candidates)
-
         def dfs(s, u, t):
             if s == target:
-                ans.append(t.copy())
+                ans.append(t[:])
                 return
             if s > target:
                 return
-            for i in range(u, n):
+            for i in range(u, len(candidates)):
                 c = candidates[i]
                 t.append(c)
                 dfs(s + c, i, t)
                 t.pop()
 
+        ans = []
         dfs(0, 0, [])
         return ans
 ```

solution/0000-0099/0039.Combination Sum/README_EN.md

@@ -71,21 +71,19 @@ DFS.
 ```python
 class Solution:
     def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
-        ans = []
-        n = len(candidates)
-
         def dfs(s, u, t):
             if s == target:
-                ans.append(t.copy())
+                ans.append(t[:])
                 return
             if s > target:
                 return
-            for i in range(u, n):
+            for i in range(u, len(candidates)):
                 c = candidates[i]
                 t.append(c)
                 dfs(s + c, i, t)
                 t.pop()
 
+        ans = []
         dfs(0, 0, [])
         return ans
 ```

solution/0000-0099/0039.Combination Sum/Solution.py

@@ -1,19 +1,17 @@
 class Solution:
     def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
-        ans = []
-        n = len(candidates)
-
         def dfs(s, u, t):
             if s == target:
-                ans.append(t.copy())
+                ans.append(t[:])
                 return
             if s > target:
                 return
-            for i in range(u, n):
+            for i in range(u, len(candidates)):
                 c = candidates[i]
                 t.append(c)
                 dfs(s + c, i, t)
                 t.pop()
 
+        ans = []
         dfs(0, 0, [])
         return ans

solution/0700-0799/0797.All Paths From Source to Target/README.md

@@ -92,18 +92,16 @@ DFS：
 ```python
 class Solution:
     def allPathsSourceTarget(self, graph: List[List[int]]) -> List[List[int]]:
-        ans = []
-
         def dfs(t):
             if t[-1] == len(graph) - 1:
-                ans.append(t.copy())
+                ans.append(t[:])
                 return
-
             for v in graph[t[-1]]:
                 t.append(v)
                 dfs(t)
                 t.pop()
-
+        
+        ans = []
         dfs([0])
         return ans
 ```

solution/0700-0799/0797.All Paths From Source to Target/README_EN.md

@@ -88,18 +88,16 @@ DFS:
 ```python
 class Solution:
     def allPathsSourceTarget(self, graph: List[List[int]]) -> List[List[int]]:
-        ans = []
-
         def dfs(t):
             if t[-1] == len(graph) - 1:
-                ans.append(t.copy())
+                ans.append(t[:])
                 return
-
             for v in graph[t[-1]]:
                 t.append(v)
                 dfs(t)
                 t.pop()
-
+        
+        ans = []
         dfs([0])
         return ans
 ```