20261009

I went on a date with my wife at Valley Fair Mall

work
bought a Dyson hair dryer
LeetCode
- 127. Word Ladder
  - leverage the constraint with string.ascii_lowercase, pattern matching
- 58. Length of Last Word (C++)
  - #include <algorithm>, std::max(), backwards, static_cast<int>()
exercises, calorie log

#include <string>

class Solution {
public:
    int lengthOfLastWord(std::string s) {
        int i = static_cast<int>(s.size() - 1);
        while (0 <= i && s[i] == ' ') { --i; }
        int length = 0;
        while (0 <= i && s[i] != ' ') {
            --i;
            ++length;
        }
        return length;
    }
};

20261008

My wife passed all 4 exams of CPA! Congratulations! Now I’ll be a stay-at-home-husband…

!LeetCode
- 224. Basic Calculator
  - first AC
bought flowers for my wife
run, workout, diet log
work (hard)

20261007

!customer visit
work
- SOR (System of Record)
LeetCode
- 295. Find Median from Data Stream
  - two heaps, sqrt decomposition

20261006

I felt a little envious when someone else in my study group got a job at a Big Tech company, but on second thought, health is what matters most, and I have a lovely wife.

!LeetCode
- 224. Basic Calculator
work (somewhat hard)
flight to Orange County
Where The Clawdads Sing
walking, diet log

20261005

!LeetCode
- 224. Basic Calculator
  - TLE but managed to write a brute-force solution
work (somewhat hard)
exercises, calorie log
LeetCode
- 127. Word Ladder
- 20. Valid Parentheses (C++)
  - …evaluating both operands can occasionally be useful when the expressions have side effects:…That said, deliberately relying on this with booleans is fairly uncommon and can make code harder to understand. If your intention is “I need both operations to happen,” it’s usually clearer to write them separately:
- 111. Minimum Depth of Binary Tree (code review)
- 112. Path Sum (code review)

20261004

!LeetCode
- 127. Word Ladder
  - understood the pattern matching approach, practiced an approach to iterate English lowercase
  - created a pull request
  - Python may reuse (intern/cache) some immutable objects to save memory, but doing so for every object would add lookup, bookkeeping, and lifetime-management overhead.
my wife’s driving practice
LeetCode
- 342. Power of Four (C++)
  - recursion, iteration, bit mask, modulo
- 9. Palindrome Number (C++)
exercises, diet log

20261003

Today was the most relaxing day I’ve had in a while.

my wife’s driving practice
watched a movie with my wife
exercises

20261002

I ate too much in the last 3 days. will try to go back to the normal state

Today’s Stretches

LeetCode
- 127. Word Ladder
  - time/space complexity analysis

Daily Reps

work
LeetCode
- 208. Implement Trie (Prefix Tree) (code review)
- 342. Power of Four (C++)
  - normal for loop, recursion, bit mask, mod

class Solution {
public:
    bool isPowerOfFour(int n) {
        if (n <= 0) { return false; }
        if (n == 1) { return true; }
        if (n % 4 != 0) { return false; }
        return isPowerOfFour(n / 4);
    }
};

20261001

Today’s Stretches

LeetCode
- 342. Power of Four (C++)

Daily Reps

work
highway drive with my wife
flu shot + COVID booster @Kaiser Permanente
LeetCode
- 295. Find Median from Data Stream
  - two heaps, square root decomposition + tried math.ceil()
- 231. Power of Two (C++)
jog & walk with my wife

class Solution {
public:
    bool isPowerOfTwo(int n) {
        if (n <= 0) { return false; }

        while (1 < n) {
            if (n % 2 == 1) { return false; }
            n = n / 2;  // n /= 2;
        }

        return true;
    }
};

class Solution {
public:
    bool isPowerOfTwo(int n) {
        if (n <= 0) { return false; }
        return (n & (n - 1))  == 0;
    }
};

class Solution {
public:
    bool isPowerOfFour(int n) {
        const int MASK = 0x55555555;

        if (n <= 0) { return false; }
        if ((n & MASK) != n) { return false; }
        return (n & (n - 1)) == 0;
    }
};

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