刷题记录帖

937. Reorder Data in Log Files
use comparator. practice.


125. Valid Palindrome
finish two pointers technique

learn to finish alphanumeric technique.


157. Read N Characters Given Read4
API?

415. Add Strings
finish this .
compare reading about adding
58. Length of Last Word
   if(s==" "){return 0;}
  if(arr==null){return 0;}
when you want to say there is nothing in it.

43. Multiply Strings
use graph

use AC solution.
finish
231. Power of Two
done
while(n%2==0){
            n=n/2;
        }
Bitwise Operators : not understand

326. Power of Three
need to understand more ways.

342. Power of Four
need to understand more ways.

周五
6. ZigZag Conversion
studied first approach

周六休假一天

22. Generate Parentheses

not done ， hard to understand

937. Reorder Data in Log Files
Public String [ ] split ( String regex, int limit )
limit > 0 : If this is the case then the pattern will be applied at most limit-1 times, the resulting  array’s length will not be more than n, and the resulting array’s last entry will contain all input beyond the last matched pattern.
limit < 0 : In this case, the pattern will be applied as many times as possible, and the resulting array can be of any size.
limit = 0 : In this case, the pattern will be applied as many times as possible, the resulting array can be of any size, and trailing empty strings will be discarded.


comparater：
class IntComparator<T> implements Comparator<T> {
    public int compare(T a, T b) {
        int num1 = (Integer)a;
        int num2 = (Integer)b;
        
        if(num1 > num2) { //如果 a>b，根据自定义规则 a 应该在前面，即自定义规则中 a “小于” b，故此时返回负值
            return -1;
        } else if(num1 < num2) {
            return 1;
        } else {
            return 0;
        }
    }
}

Studied backtracking. Need to find resource to help me understand it.

136. Single Number
boolean containsKey(Object key): Used to return True if for a specified key, mapping is present in the map.
boolean containsValue(Object value): Used to return true if one or more key is mapped to a specified value.
boolean isEmpty(): Used to check whether the map is empty or not. Returns true if the map is empty.
Object get(Object key): It is used to retrieve or fetch the value mapped by a particular key.
int size(): It is used to return the size of a map.
Object put(Object key, Object value): It is used to insert a particular mapping of key-value pair into a map.

hashset
boolean add(E e): Used to add the specified element if it is not present, if it is present then return false.
boolean contains(Object o): Used to return true if an element is present in set.
boolean isEmpty(): Used to check whether the set is empty or not. Returns true for empty and false for non-empty condition for set.
int size(): Used to return the size of the set.

相对应的ti

202. Happy Number
studied one method. Not finish

260. Single Number III
Approach 2: Two bitmasks not finish

202. Happy Number

finish one way, continuew with some other way. think reversly.

And understand the resursive way.

349. Intersection of Two Arrays
not finish yet

周四面试zoox 累瘫

242. Valid Anagram
use two set to compare。 not right. Why?
need to study more

Arrays.equals() ： check whether two arrays are equal or not
char[] str1 = s.toCharArray();

Practice tmr.
  for(int i = 0; i < s.length(); i++){
            sMap.put(s.charAt(i), sMap.getOrDefault(s.charAt(i), 0) + 1);
        }

349. Intersection of Two Arrays
use two set to compare.
Arrays copyOf()
copyOf(int[] original, int newLength)

set1.retainAll(set2);

266. Palindrome Permutation

finish one method, study more.

49. Group Anagrams
notfinish yet

438. Find All Anagrams in a String
check sliding winfdow.

补充内容 (2019-10-8 02:19):
49. Group Anagrams finish