# 491. Increasing Subsequences 递增子序列

@TOC

## # 题目描述

Given an integer array, your task is to find all the different possible increasing subsequences of the given array, and the length of an increasing subsequence should be at least 2 .

``````Example:
Input: [4, 6, 7, 7]
Output: [[4, 6], [4, 7], [4, 6, 7], [4, 6, 7, 7], [6, 7], [6, 7, 7], [7,7], [4,7,7]]
``````

Note:

1. The length of the given array will not exceed 15.
2. The range of integer in the given array is [-100,100].
3. The given array may contain duplicates, and two equal integers should also be considered as a special case of increasing sequence.

## # 解题方法

dfs做法：

``````class Solution(object):
def findSubsequences(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
res = set()
self.dfs(nums, 0, res, [])
return map(list, res)

def dfs(self, nums, index, res, path):
if len(path) >= 2:
for i in range(index, len(nums)):
if not path or nums[i] >= path[-1]:
self.dfs(nums, i + 1, res, path + [nums[i]])
``````

``````class Solution(object):
def findSubsequences(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
dp = set()
for n in nums:
for y in list(dp):
if n >= y[-1]: