*LeetCode--Most Common Word

Posted SkyeAngel

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了*LeetCode--Most Common Word相关的知识,希望对你有一定的参考价值。

Given a paragraph and a list of banned words, return the most frequent word that is not in the list of banned words.  It is guaranteed there is at least one word that isn‘t banned, and that the answer is unique.

Words in the list of banned words are given in lowercase, and free of punctuation.  Words in the paragraph are not case sensitive.  The answer is in lowercase.

Example:
Input: 
paragraph = "Bob hit a ball, the hit BALL flew far after it was hit."
banned = ["hit"]
Output: "ball"
Explanation: 
"hit" occurs 3 times, but it is a banned word.
"ball" occurs twice (and no other word does), so it is the most frequent non-banned word in the paragraph. 
Note that words in the paragraph are not case sensitive,
that punctuation is ignored (even if adjacent to words, such as "ball,"), 
and that "hit" isn‘t the answer even though it occurs more because it is banned.

 

需要注意的点:

1.在java中防止转义字符是 要使用 \ 不是 /

2.还有就是如果字符串中包含不需要的某几个字符时,可以使用replaceAll()方法去掉

public String replaceAll(String regex,
                         String replacement)
其中第一个参数是一个正则表达式,表示替换和regex中相匹配的所有字符串。

3.将数组转成集合List需要借助Arrays工具类

4.map的一种简单判断是否存在,且放入键值对的方法:

map.put(word, map.getOrDefault(word, 0) + 1);

map.getOrDefault(key, defaultValue)“键”没找到的时候返回提供的默认值,而且还会将键和默认值增加到调用的map中。
返回的是value值

 

 

class Solution {
     public String mostCommonWord(String paragraph, String[] banned) {
        if(paragraph == null || paragraph.length() == 0) return null;
        String newStr = paragraph.toLowerCase();
        Set<Character> set = new HashSet<>();
        set.add(‘.‘);
        set.add(‘,‘);
        set.add(‘;‘);
        set.add(‘?‘);
        set.add(‘!‘);
        set.add(‘\‘‘);
        System.out.println(newStr);

        HashMap<String, Integer> map = new HashMap<>();
        String[] str = newStr.split( " " );
        for(int i = 0; i < str.length; i++){
            if(set.contains(str[i].charAt(str[i].length() - 1))){
                str[i] = str[i].substring(0, str[i].length() - 1);
            }
            if(!Arrays.asList( banned ).contains(str[i])){
                if(map.containsKey(str[i])){
                    map.put(str[i], map.get(str[i]) + 1);
                } else{
                    map.put(str[i], 1);
                }
            }
        }

        int max = Integer.MIN_VALUE;
        String res = new String();
        for(Map.Entry<String, Integer> entry : map.entrySet()){
            if(entry.getValue() > max){
                max = entry.getValue();
                res = entry.getKey();
            }
        }
        return res;
    }
}

  

 

优化之后的:

 

class Solution {
     public String mostCommonWord(String paragraph, String[] banned) {
        if(paragraph == null || paragraph.length() == 0) return null;
        String[] str = paragraph.replaceAll("[,.?;‘!]", "").toLowerCase().split(" ");
         List<String> newBanned = Arrays.asList(banned);
        HashMap<String, Integer> map = new HashMap<>();
        for(int i = 0; i < str.length; i++){
            if(!newBanned.contains(str[i])){
                map.put(str[i], map.getOrDefault(str[i], 0) + 1);
            }
        }

        String res = null;
        for(String s : map.keySet()){
            if(res == null || map.get(s) > map.get(res)){
                res = s;
            }
        }
        return res;
    }
}

  





以上是关于*LeetCode--Most Common Word的主要内容,如果未能解决你的问题,请参考以下文章

LeetCode Most Frequent Subtree Sum

LeetCode - Most Frequent Subtree Sum

[LeetCode] Most Frequent Subtree Sum 出现频率最高的子树和

[LeetCode] Most Profit Assigning Work 安排最大利润的工作

Oracle 创建视图(View)实例

Maximo Anywhere 搜索 WO