NC_85_MIN_STRING NC_88_KTH NC_86_findElement

package org.example.interview.practice;

import java.util.Comparator;
import java.util.PriorityQueue;

/**
 * @author xianzhe.ma
 * @date 2021/8/22
 */

public class NC_85_MIN_STRING {
    public String minString (String[] strs) {
        // write code here
        if(strs == null || strs.length < 1) {
            return null;
        }
        // 重载比较函数
        PriorityQueue<String> queue = new PriorityQueue<>(new Comparator<String>() {
            public int compare(String s1, String s2) {
                // 保证 s1 + s2 > s2 + s1 时，返回值大于0，否则返回值小于0
                // 保证queue中越靠近队头的元素，字典序越小
                return (s1 + s2).compareTo(s2 + s1);
            }
        });
        // 放入队列中排好序
        for(String str : strs) {
            queue.offer(str);
        }
        StringBuilder res = new StringBuilder();
        // 重新从队列中获取
        while(queue.size() > 0) {
            res.append(queue.poll());
        }
        return res.toString();
    }
}

package org.example.interview.practice;

import java.util.Arrays;
import java.util.Comparator;
import java.util.PriorityQueue;

/**
 * @author xianzhe.ma
 * @date 2021/7/9
 * 注意是找第K大的数，而不是排序过后按照从小到大的第k-1下标比如 10，10，9，9，8 如果K=3，返回是9 因为第一第二大是10，10 第三大就是9
 * 如果是查找按照从小到大顺序的第K个数，那就用大顶堆
 */

public class NC_88_KTH {

//        public static int findKth(int[] a, int n, int K) {
//            // write code here
//            PriorityQueue<Integer> queue = new PriorityQueue<>( new Comparator<Integer>() {
//
//                @Override
//                public int compare(Integer o1, Integer o2) {
//
//                    return o2-o1;
//                }
//            });
//            for (int i=0;i<K;i++) {
//                queue.offer(a[i]);
//            }
//
//            for (int j=K;j<n;j++) {
//                Integer value = queue.peek();
//                if (a[j]<value) {
//                    queue.poll();
//                    queue.offer(a[j]);
//                }
//            }
//
//            return queue.poll();
//        }

    public static int findKth(int[] a, int n, int K) {
        // write code here
        //小根堆
        PriorityQueue<Integer> pq = new PriorityQueue<>() ;

        for (int i=0;i<K;i++) {
            pq.add(a[i]) ;
        }

        for(int i = K ; i < n ; i++)
        {
           if(a[i] > pq.peek()){
                pq.poll() ;
                pq.add(a[i]) ;
            }
        }
        return pq.peek() ;

    }

        public static void main (String[] args) {
            int[] arr = {5,7,4,2,10,8,22,44,1};
//            int[] arr = {1332802,1177178,1514891,871248,753214,123866,1615405,328656,1540395,968891,1884022,252932,1034406,1455178,821713,486232,860175,1896237,852300,566715,1285209,1845742,883142,259266,520911,1844960,218188,1528217,332380,261485,1111670,16920,1249664,1199799,1959818,1546744,1904944,51047,1176397,190970,48715,349690,673887,1648782,1010556,1165786,937247,986578,798663};
            Arrays.sort(arr);
            System.out.println(arr[3]);
            int value = findKth(arr, arr.length, 4);
            System.out.println(value);
        }
}

import java.util.*;

public class NC_86_FIND_ELEMENT{
    public int[] findElement(int[][] mat, int n, int m, int x) {
        // write code here
        int[] result = new int[2];
    int row = 0;
    int col = m - 1;
    while(row < n && col >= 0) {
        if(mat[row][col] == x) {
            result[0] = row;
            result[1] = col;
            break;
        }
        if(x > mat[row][col]) {
            row ++;
        } else {
            col --;
        }
    }
    return result;
    }
}