Combination Sum

def combinationSum(candidates, target):
    res = []
    
    def dfs(i, cur, total):
        if total == target:
            res.append(cur.copy())
            return
        if i >= len(candidates) or total > target:
            return
            
        cur.append(candidates[i])
        dfs(i, cur, total + candidates[i])
        
        cur.pop()
        dfs(i + 1, cur, total)
        
    dfs(0, [], 0)
    return res