215. Kth Largest Element in an Array

题目

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

示例1:

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Input: [3,2,1,5,6,4] and k = 2
Output: 5

示例2:

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Input: [3,2,3,1,2,4,5,5,6] and k = 4
Output: 4

提示:

  1. You may assume k is always valid, 1 ≤ k ≤ array’s length.

解法

解法一:

排序,直接返回nums[nums.length - k]

JAVA

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class Node {
private char c;
private int times;

public Node(char c, int times) {
this.c = c;
this.times = times;
}

public char getC() {
return c;
}

public void setC(char c) {
this.c = c;
}

public int getTimes() {
return times;
}

public void setTimes(int times) {
this.times = times;
}
}
public String frequencySort(String s) {
int[] chars = new int[256];
for (char c : s.toCharArray()) {
chars[c]++;
}

PriorityQueue<Node> charNodes = new PriorityQueue<>((a, b) -> b.getTimes() - a.getTimes());
for (int i = 0;i < 256;i++) {
if (chars[i] == 0) {
continue;
}

Node node = new Node((char) i, chars[i]);
charNodes.add(node);
}

StringBuilder sb = new StringBuilder();
while (!charNodes.isEmpty()) {
Node node = charNodes.poll();
int total = node.getTimes();
while (total > 0) {
sb.append(node.getC());
total--;
}
}
return sb.toString();
}
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