经典一题多解

Hashset / Hashmap

• Two sum

  • O(NlogN) Sort + Two pointer

  • O(N) Hashmap

Heap

• Kth largest element in an array

  • O(NlogK) Heap

  • O(N) average Quicksort

• K-way merge

  • O(NKlogK) Divide and conquer

  • O(NKlogK) Heap

Subsequence / Subarray

• Maximum subarray

  • O(N²) Presum

  • O(NlogN) Divide and conquer

  • O(N) DP

• Longest increasing subsequence (LIS)

  • O(N²) DP

  • O(NlogN) Binary search

• Longest palindrome substring

  • O(N²) DP

  • O(N²) Expand from center