# Summary_April

## Plan x Reality

| # | Category | Title | Note | Start Date | End Date |
|--------| -------- | -------- | -------- | -------- | -------- |
| 1| Bit Manipulation | Single Number | New | 2024.04.07 |2024.04.07|
| 2| Math & Geometry |Multiply Strings | Review [Microsoft]()| 2024.04.08 |2024.04.16|
| 3| Math & Geometry |Pow(x, n) | Review |2024.04.09 |2024.04.14|
| 4| Math & Geometry | Plus One |Review [Microsoft]()|2024.04.11| 2024.04.16 |
| 5| Math & Geometry | Happy Number |Review |- | 2024.04.15 |
| 6| Math & Geometry | Reverse Integer |Review |2024.04.13 |2024.04.14|

### LeetCode Profile
`https://leetcode.com/Yu_135/`

| Date | Solved | Remark |
| -------- | -------- | -------- |
| 2024.04.07 | 187 | |
| 2024.04.07 | 188 | ADD `Single Number` |

#### NeetCode 150
`https://neetcode.io/practice`
| Date | Solved | Remark |
| -------- | -------- | -------- |
| 2024.04.07 | 144 / 150 | |
| 2024.04.07 | 145 / 150 | ADD `Single Number` |
| 2024.04.14 | 146 / 150 | ADD `Reverse Integer` |
| 2024.04.15 | 148 / 150 | ADD `Happy Number` |
| 2024.04.16 | 149 / 150 | ADD `Plus One` |

##### Plus One

:::spoiler

:::

##### Multiply strings

:::spoiler

class Solution:
    def multiply(self, num1: str, num2: str) -> str:
        if "0" in [num1, num2]:
            return "0"

        res = [0] * (len(num1) + len(num2))
        num1, num2 = num1[::-1], num2[::-1]
        print("num1,num2:",num1,num2)
        for i1 in range(len(num1)):
            for i2 in range(len(num2)):
                print("d1xd2:",int(num1[i1]),int(num2[i2]))
                digit = int(num1[i1]) * int(num2[i2])
                res[i1 + i2] += digit
                res[i1 + i2 + 1] += res[i1 + i2] // 10
                res[i1 + i2] = res[i1 + i2] % 10

        res, beg = res[::-1], 0
        while beg < len(res) and res[beg] == 0:
            beg += 1
        res = map(str, res[beg:])
        return "".join(res)

:::

:::spoiler
### with explain

class Solution:
    def multiply(self, num1: str, num2: str) -> str:
        if "0" in [num1, num2]:
            return "0"

        # max len : 999 x 999 = 998 001
        res = [0] * (len(num1) + len(num2))
        # from 0 to process 
        num1, num2 = num1[::-1], num2[::-1]
        print("num1,num2:",num1,num2)
        for i1 in range(len(num1)):
            for i2 in range(len(num2)):
                print("d1xd2:",int(num1[i1]),int(num2[i2]))
                # digit1 x digit2  
                digit = int(num1[i1]) * int(num2[i2])
                # 累加至 res 的 current digit
                res[i1 + i2] += digit
                # 進位 
                res[i1 + i2 + 1] += res[i1 + i2] // 10
                # update current digit 
                res[i1 + i2] = res[i1 + i2] % 10

        res, beg = res[::-1], 0
        # search for non-zero digit
        while beg < len(res) and res[beg] == 0:
            beg += 1
        # trasfer all int to str     
        res = map(str, res[beg:])
        # string list to string 
        return "".join(res)

        

:::