【Lintcode】1613. Highest frequency IP

题目地址：

https://www.lintcode.com/problem/highest-frequency-ip/description

给定一个字符串数组，求其中出现最多的那个字符串。题目保证答案唯一。用一个哈希表存每个字符串出现了多少次，同时用一个int变量记录出现最多的次数。遍历完后将哈希表里出现次数最多的那个字符串挑出来即可。代码如下：

import java.util.HashMap;
import java.util.Map;public class Solution {/*** @param ipLines: ip address* @return: return highestFrequency ip address*/public String highestFrequency(String[] ipLines) {// Write your code hereint maxFrequency = 0;Map<String, Integer> frequencies = new HashMap<>();for (String ipLine : ipLines) {frequencies.put(ipLine, frequencies.getOrDefault(ipLine, 0) + 1);maxFrequency = Math.max(frequencies.get(ipLine), maxFrequency);}for (Map.Entry<String, Integer> entry : frequencies.entrySet()) {if (entry.getValue() == maxFrequency) {return entry.getKey();}}return "";}
}

时空复杂度 $O(n)$。