(A) string
1, substring: sequences of any consecutive string of characters called a sub-string of the string
Note: the empty string belongs substring
2, character strings are not identical: n string consisting of characters, assume each character is different, asked how many substrings
Answer: n-(n-+. 1) / 2 +. 1
Tip: The individual characters are not the same
analysis:
sub-string of characters comprises a total of n number of
sub-character string comprising two co the n-1
contains three characters common substrings two n-2
comprises four sub-character total n-3 series th
......
sub-string containing n characters of 1
empty string a
sum: total number of sub-strings: 1 + 2 + 3 +. . . + n + 1 (the empty string) = n (n + 1) / 2 + 1
Example application: If the string S = 'software', the number of which is a substring ()
Analytical: n (n + 1) / 2 + 1 = 8 (8 + 1) / 2 + 1 = 37
3, character string duplicates: all non-empty string www.qq.com strings (two strings based on a count only if the contents are the same) number is ()
Answer: 50
Note: presence of the same characters, calculated as the total number of repetition subtracted number, i.e. n (n + 1) / 2 + 1- repeat number
Analysis: comprising repeating substring Total: n (n + 1) / 2 + 1 = 10 (10 + 1) / 2 + 1 = 55, minus the repetition: 2 w, 1 th ww, 1 th q, 1 th ., so that a total of 55-5 = 50
Questions:
in-place standing: itself O (1 space); recursion, stack space may not be considered
Issues related to the place: a string rotate left and right movement
Sliding window: to achieve complexity of O (n) time; complexity of O (1) space
Related rules
Match (violence): KMP
Manacher: linear time seeking palindromic substring
(B) algorithm
First, the dictionary order
Second, the operation is simple: insert, delete characters, rotation
1. The copy and character replacement
2. Flip word
Third, the rule judgment (the Roman numeral converter, is a valid integer, floating point)
Fourth, the digital arithmetic (addition of large numbers, binary addition)
Fifth, sorting, exchange (partition process)
1.0-1 exchange
Question: put a 0-1 string sorting, you can swap any two locations, and asked the least number of exchanges?
2. exchange asterisk
1 idea: fast row partition, will change the numerical order
Ideas 2: backwards copy, in numerical order will not change
Six Character Count (hash): anagram
Seven, matching (regular expressions, the whole string matching, the KMP, determination period)
Eight, dynamic programming (LCS, edit distance, the longest palindrome substring)
IX search (word conversion, permutations)
Ten, sliding window
1. substring anagram
Ideas 1: hash
references:
[1] [Google] algorithms Ali interview succinctly _ beep beep miles miles (゜-゜) zu ro Cheers ~ -bilibili