# [Study][Python] lambda

This is a note for python study.

The Lambda can use a function by one line code.

For example, below add function is two lines as below.

`def add_up(x,y):    return x+y`

We can re-write one line as below.

`add_up = lambda x, y:x+y`

The result is the same.

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# [crypto] Crypto exchange

In recent months, I join the crypto investigation. Below is my crypto exchange list.

1. Max exchange

If you use TWD, you can buy USDT and send them to other exchange to buy other coins such as BTC, ETH… This is for rookie.

Staking Max coin apy is 2% to 5%.

2. Binance

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# [LeetCode]#1822. Sign of the Product of an Array

Environment: Python 3.8

Key technique: for, if

There is a function `signFunc(x)` that returns:

• `1` if `x` is positive.
• `-1` if `x` is negative.
• `0` if `x` is equal to `0`.

You are given an integer array `nums`. Let `product` be the product of all values in the array `nums`.

Return `signFunc(product)`.

Example 1:

`Input: nums = [-1,-2,-3,-4,3,2,1]Output: 1Explanation: The product of all values in the array is 144, and signFunc(144) = 1`

Analysis:

1. init ans=1
2. ans=ans x nums[i] by using loop
3. if ans >0, return 1
4. if ans <0, return -1
5. if ans==0, return 0

Solution:

`class Solution:    def arraySign(self, nums):        ans=1        for i in range(len(nums)):            ans=ans*nums[i]        if ans >0:            return 1        if ans <0:            return -1        if ans ==0:            return 0`

Submissions:

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# [LeetCode]#2124. Check if All A’s Appears Before All B’s

Environment: Python 3.8

Key technique: if

Given a string `s` consisting of only the characters `'a'` and `'b'`, return `true` if every `'a'` appears before every `'b'` in the string. Otherwise, return `false`.

Example 1:

`Input: s = "aaabbb"Output: trueExplanation:The 'a's are at indices 0, 1, and 2, while the 'b's are at indices 3, 4, and 5.Hence, every 'a' appears before every 'b' and we return true.`

Analysis:

1. check pattern “ba” is matched with s.
2. If yes, return False. Else, return True.

Solution:

`class Solution:    def checkString(self, s):        if "ba" in s:            return False        else:            return True`

Submissions:

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# [LeetCode]#2119. A Number After a Double Reversal

Environment: Python 3.8

Key technique: str(), int()

Reversing an integer means to reverse all its digits.

• For example, reversing `2021` gives `1202`. Reversing `12300` gives `321` as the leading zeros are not retained.

Given an integer `num`, reverse `num` to get `reversed1`, then reverse `reversed1` to get `reversed2`. Return `true` if `reversed2` equals `num`. Otherwise return `false`.

Example 1:

`Input: num = 526Output: trueExplanation: Reverse num to get 625, then reverse 625 to get 526, which equals num.`

Analysis:

1. Convert input to string format and reverse it
2. Convert it to int format.
3. Convert it to a string format and reverse it.
4. If input equal converted result, return pass.
5. Else, return Fail.

Solution:

`class Solution:    def isSameAfterReversals(self, num):        temp=str(num)        temp=int(temp[::-1])        temp=str(temp)        temp=temp[::-1]        if int(temp) ==num:            return True        else:            return False`

Submissions:

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# [LeetCode]#2108. Find First Palindromic String in the Array

Environment: Python 3.8

Key technique: for, [::-1]

Given an array of strings `words`, return the first palindromic string in the array. If there is no such string, return an empty string `""`.

A string is palindromic if it reads the same forward and backward.

Example 1:

`Input: words = ["abc","car","ada","racecar","cool"]Output: "ada"Explanation: The first string that is palindromic is "ada".Note that "racecar" is also palindromic, but it is not the first.`

Analysis:

1. Reverse input string
2. If string == reversed string, return it.
3. If no string and reversed string is equal, return ‘’

Solution:

`class Solution:    def firstPalindrome(self, words):        for i in words:            if i==i[::-1]:                return i        return ''`

Submissions:

Reference:

https://leetcode.com/problems/find-first-palindromic-string-in-the-array/discuss/1639462/Python-99-faster-Simple-Solution

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## Fatboy Slim

Interesting in any computer science.