657. Judge Route Circle
Simple, no need to comment
[LeetCode] Challenge log 461
461. Hamming Distance
https://leetcode.com/problems/hamming-distance/description/
- Use bitwise operation XOR (1 if the bit is different).
- Count the number of 1 bits ( exactly as NO.191).
[LeetCode] Challenge log 535
535. Encode and Decode TinyURL
https://leetcode.com/problems/encode-and-decode-tinyurl/description/
- Solution1: Use increasing numbers to mark tiny urls; actual urls are saved in a indexed list. (If want letters, can transfer the number into 62-based)
- Alternative: Genrate random 6-places string as tiny url. Two dictionaries to allow mapping in two ways and no duplicate.
[LeetCode] Challenge log 804
804. Unique Morse Code Words
https://leetcode.com/problems/unique-morse-code-words/description/
- Use set to maintain unique words.
- String is hashable.
[LeetCode] Challenge log 771
771. Jewels and Stones
https://leetcode.com/problems/jewels-and-stones/description/
- Use hashing to achieve O(n+m).
- Use set as a dict without value to save space
[LeetCode] Challenge log 215
215. Kth Largest Element in an Array
https://leetcode.com/problems/kth-largest-element-in-an-array/description/
- Use len(k)-array to save the largest k elements
- Through binary search insertion to keep the array sorted.
[LeetCode] Challenge log 152
152. Maximum Product Subarray
https://leetcode.com/problems/maximum-product-subarray/description/
It is a DP problem. Similar to 53.
[LeetCode] Challenge log 53
53. Maximium Subarray
https://leetcode.com/problems/maximum-subarray/description/
It is mainly a DP problem.