leetcode – string

• edit distance: DP
• generate paranthes: Iterative Recursive
• integer to english words: Unit(every 3) Recurvise
• interleaving string: Iterative Recusive/DP
• longest valid parenthes: Stack存分界符 (注意’)’pop分情况)
• minimum window substring: 双指针法。1，找到满足子串；2，移动start使之成为最短
• palindrom pairs: 分3种情况回文, O(n)空间换时间从O($n^2$)为O(n)
• shortest palindrom: 找到最长回文子串即可
• regular expression matching: DP
• wilcard matching: DP
• valid number: regexp/NFS
• scramble string: Substring Recursive
• word ladder II: 构建非重复前向路径