4Sum; Combination Sum

4Sum
Class solution (Object):
def foursum (self, Nums, target):
Nums.sort ()
results = []
Self.findnsum (Nums, Target, 4, [], results)
return results

def findnsum (self, nums, target, N, result, results):
If Len (nums) < n or N < 2:return

# Solve 2-sum
if N = = 2:
L,r = 0,len (nums)-1
While L < r:
If NUMS[L] + nums[r] = = target:
Results.append (Result + [nums[l], Nums[r])
L + = 1
R-= 1
While L < r and Nums[l] = = Nums[l-1]:
L + = 1
While R > L and nums[r] = = Nums[r + 1]:
R-= 1
Elif Nums[l] + Nums[r] < target:
L + = 1
Else
R-= 1
Else
For I in range (0, Len (nums)-n+1): # Careful about Range
If target < Nums[i]*n or Target > nums[-1]*n: # Take advantages of sorted list
Break
If i = = 0 or i > 0 and nums[i-1]! = Nums[i]: # recursively reduce N
Self.findnsum (nums[i+1:], target-nums[i], N-1, Result+[nums[i]], results)

Combination sum

Combinationsum (candidates, target):
res = []
Candidates.sort ()
Self.dfs (candidates, target, 0, [], RES)
Res

DFS (self, nums, target, index, PATH, res):
Target < 0:
# backtracking
target = = 0:
Res.append (PATH)
Return
Xrange (index, Len (nums)):
Self.dfs (Nums, target-nums[i], I, path+[nums[i]], RES)

Result

4Sum; Combination Sum