String

About string

• 长度为n的字符串，子串数量是 n * (n + 1) / 2
• Python
  • convert char to number rec[ord(s[left]) - ord('A')]
  • covert number to char chr(i + ord('A'))
  • sorted(string) get a list of char
  • s[::-1] reverse the string, but time complexity is O(n)
  • s.strip()去掉开头和结尾的空格
  • fruits = s.split(",")默认按空格分割
  • list(string) -> string "/".join(stack)
  • string和int互相转化：num = int(s), s = str(num)
• C++
  • string / char merge:
    • 两个string: string merged = str1 + str2 or str1.push_back(str2)
    • string + char: str.push_back(c)
    • 两个char -> 转化为两个或一个string
  • char -> string: string s(1, c); merged += c2 // 用 c1 初始化一个长度为 1 的字符串 merged
  • int -> string: str = to_string(num);
  • 0 -> 'A': string(1, 'A' + 0)
  • string -> int: num = stoi(str); "123" -> 123
  • char -> int: (int)c; 判断char是否是数字: if (isdigit(c))
  • int -> char: (char)num eg. char(65) -> 'A'
  • vector -> string:
    • vector<char> s = {'H', 'e', 'l', 'l', 'o'}; string result(s.begin(), s.end());
    • vector<string> s = {"Hello", " ", "World"}; string result = accumulate(s.begin(), s.end(), string());
  • reverse: reverse(str.begin(), str.end());

What I have done

5. Longest Palindromic Substring
49. Group Anagrams
467. Unique Substrings in Wraparound String

Template

for token in input.split('\n'):
    depth = token.count('\t')
    token = token.replace('\t', '')

What I have done

388. Longest Absolute File Path

string in C++

list<char> stack;
string str(stack.begin(), stack.end()); // [ , )

What I have done

316. Remove Duplicate Lettersgreedy

istringstream iss(expression);
int a; int b; char _;
while (iss >> a >> _ >> b) {}

What I have done

592. Fraction Addition and Subtraction