Leetcode里的常用函数

最新推荐文章于 2024-05-10 14:01:59 发布

LSKxueJava

最新推荐文章于 2024-05-10 14:01:59 发布

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分类专栏：笔记文章标签： java

本文链接：https://blog.youkuaiyun.com/qq_43063585/article/details/114745889

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本文汇总了Java编程中常用的代码片段及技巧，包括数组操作、字符串处理、集合管理和映射使用等，适合各阶段开发者参考学习。

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Math.max(a, b)
Arrays.sort()
s.compareTo("…")
s = s.replace(“IV”,“a”)
sb.insert()
map.getOrDefault()
Map<a, b> map = new LinkedHashMap<>();

for(Map.Entry<a, b> entry : map.entrySet()){
            if(entry.getValue()) return entry.getKey();
}

Math.abs()
num >>>= 1
List<int[]> arrayList = new ArrayList<>()
arrayList.toArray(new int[0][])
s.trim()
Deque<*> deque = new LinkedList<>()
deque.isEmpty()
deque.peekLast()
deque.removeLast()
deque.addLast()
deque.peekFirst()
deque.removeFirst()
deque.pollLast()
deque.offerLast(value)
queue.offer(value)
deque.pollFirst()
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Arrays.fill()
Integer.MAX_VALUE
Integer.MIN_VALUE
set.remove()

Map<Character, String> phoneMap = new HashMap<Character, String>() {{
            put('2', "abc");
            put('3', "def");
            put('4', "ghi");
            put('5', "jkl");
            put('6', "mno");
            put('7', "pqrs");
            put('8', "tuv");
            put('9', "wxyz");
}};

arrayList.remove()
arrayList.add()
arrayList.size()
arrayList.set()
arrayList.get()

Map<String,List<String>> map=new HashMap<>();
map.put(key,list);
return new ArrayList<List<String>>(map.values());

int[][] intervals = {{1,3},{2,6},{8,10},{15,18}}
Arrays.sort(intervals, new Comparator<int[]>(){
    public int compare(int[] interval1, int[] interval2){
        return interval1[0]-interval2[0];
    }
});

List<int[]> merged=new ArrayList<>();
。。。
return merged.toArray(new int[merged.size()][]);

Iterator iter = map.entrySet().iterator(); 
while (iter.hasNext()) { 
    Map.Entry entry = (Map.Entry) iter.next(); 
    Character key = (Character) entry.getKey(); 
    Integer val = (Integer) entry.getValue(); 
    ......
}

Set<String> set = new HashSet<>();
......
return new ArrayList<>(set);

List<Integer> list=new ArrayList();
list.addAll(list0);
return list.stream().mapToInt(Integer::valueOf).toArray();

数组、StringBuilder、map等等如何初始化也要记住。

int[][] people={{7,0},{4,4},{7,1},{5,0},{6,1},{5,2}}；
LinkedList<int[]> list = new LinkedList<>();
for (int[] i : people) {
    list.add(i[1], i);
}
return list.toArray(new int[list.size()][2]);

map.size()

Map<Character, Integer> freq=new HashMap<>();
Set<Map.Entry<Character, Integer>> entrySet=freq.entrySet();
for(Map.Entry<Character, Integer> entry : entrySet){
    int value=entry.getValue();
    nextValid.add(1);
    rest.add(value);
}

LinkedList<String> myQueue = new LinkedList<String>();  
    myQueue.add("A");  
    myQueue.add("B");  
    myQueue.add("C");  
    myQueue.add("D");  
    List<String> myList = new ArrayList<String>(myQueue);

public boolean isAnagram(String s, String t) {
        if (s.length() != t.length()) {
            return false;
        }
        char[] str1 = s.toCharArray();
        char[] str2 = t.toCharArray();
        Arrays.sort(str1);
        Arrays.sort(str2);
        return Arrays.equals(str1, str2);
}

public boolean wordBreak(String s, List<String> wordDict) {
        Set<String> wordDictSet = new HashSet(wordDict);
        ...
    }