题解 | #字符串出现次数的TopK问题#
字符串出现次数的TopK问题
http://www.nowcoder.com/practice/fd711bdfa0e840b381d7e1b82183b3ee
善用stream流，大大减少代码量
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;
public class Solution {
/**
* return topK string
* @param strings string字符串一维数组 strings
* @param k int整型 the k
* @return string字符串二维数组
*/
public String[][] topKstrings (String[] strings, int k) {
// write code here
Map<String, Long> map = Arrays.stream(strings).collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
List<String> list = Arrays.stream(strings).distinct().sorted(((o1, o2) -> map.get(o1).equals(map.get(o2)) ? o1.compareTo(o2) : map.get(o2).compareTo(map.get(o1)))).limit(k).collect(Collectors.toList());
String[][] res = new String[k][2];
for(int i = 0; i < k; i++){
res[i][0] = list.get(i);
res[i][1] = String.valueOf(map.get(list.get(i)));
}
return res;
}
} 