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Cisco 两轮面经 (全印阵容)

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yi1san3fendi 发表于 2016-7-2 14:46:53 | 显示全部楼层 |阅读模式

2016(1-3月) 码农类 硕士 全职@Cisco - 内推 - 技术电面 |Failfresh grad应届毕业生

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Cisco网上自己投过,也找人内推过,一天突然一个印度recruiter发邮件过来联系电面,也不知是哪个起了作用
两轮面试后再无消息,3个多月过去了,估计是印度人把我当作炮灰做political correctness了. 涓浜-涓夊垎-鍦帮紝鐙鍙戝竷
. more info on 1point3acres.com
第一轮:一个印度人用webex给我电话面试,开视频,出了道 Phonebook 的 OO design, 并且有一些客户要求如果Phonebook上某些人联系方式改变,会被通知;我意识到用obeserver pattern,写了java code,  通过,说会有下一轮面试.鐣欏璁哄潧-涓浜-涓夊垎鍦

第二轮:印度recruiter联系我,说onsite面试报销太麻烦(现在想起来应该是只不过准备把我当炮灰),说继续用webex video面试,但是需要一个下午时间,面试官全印阵容, 4个印度人
1. 有一堆文档,给一个单词,返回包含这个单词的所有文档路径,并且返回这些文档跟这个单词对应的instances
. from: 1point3acres.com/bbs         word ->  <docPath1, docPath2, ..., docPathn>

. 1point 3acres 璁哄潧package cisco;
import java.io.*;
import java.util.*;

public class Solution1 {//assume the doc path is unique, and we can use it as ID
    HashMap<String, HashMap<String, Integer>> wordPathHm;//<word, <docID/path, number of instances>>
    public Solution1(){
        wordPathHm = new HashMap<String, HashMap<String, Integer>>();
    }
   
    public void buildIndex(String path) throws IOException{
        Scanner doc = new Scanner(new FileReader(path));
        while(doc.hasNextLine()){. From 1point 3acres bbs
            String line = doc.nextLine();
            String[] words = line.split("\\s+");
            for(String word : words){
                if(wordPathHm.containsKey(word)){//if the word already exists, update the hashmap
                    HashMap<String, Integer> oldlist = wordPathHm.get(word);
                    Integer currCnt = oldlist.get(path);
                    oldlist.put(path, currCnt+1);
                } else {//if the word does not exist, add a new entry
                    HashMap<String, Integer> newlist = new HashMap<String, Integer>();. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴
                    newlist.put(path, 1);
                    wordPathHm.put(word, newlist);
                }
            }
        }
        doc.close();
    }. 鍥磋鎴戜滑@1point 3 acres
   
    public List<String> getDocsPaths(String word){
        List<String> paths = new ArrayList<String>();
        if(wordPathHm.containsKey(word)){
            HashMap<String, Integer> hmRecord = wordPathHm.get(word);
            for(String docPath : hmRecord.keySet()){
                paths.add(docPath);
            }
        }
        
        return paths;
    }
   
    public int getDocInstanceNum(String word, String docPath){. 1point 3acres 璁哄潧
        if(wordPathHm.containsKey(word)){
            HashMap<String, Integer> hmRecord = wordPathHm.get(word);
            if(hmRecord.containsKey(docPath)){
                return hmRecord.get(docPath);
            } else {
                return -2; //the doc does not exist
            }
        } else {
            return -1; // the word does not exist. 鐗涗汉浜戦泦,涓浜╀笁鍒嗗湴
        }        
    }

}

然后又问如果用户很多该怎么办
DHT
hash(docID/path) -> which server should be queried for this doc
    the queried server should return the path of the documents, and how many instances in each document
multiple hashmaps.鏈枃鍘熷垱鑷1point3acres璁哄潧
each hashmap return the number of instances for this key word, and add the count  together

.鏈枃鍘熷垱鑷1point3acres璁哄潧

2. 问了操作系统调度问题,我刚好看了一点
Completely Fair Scheduler   Linux 2.6
we have different priority weights for different tasks
it is difficult for us to predict how much time

previous exectuion time
virtual running time(vrt) = already execution time/ priority weights
. from: 1point3acres.com/bbs
build red-black tree -> an approximately balanced binary search tree
if vrt is smaller , it means it should be assigned to the processor earlier
start from leftmost nodes
. 鍥磋鎴戜滑@1point 3 acres
               18
        12           26. more info on 1point3acres.com
    4        16     20    28

又问top K words
package cisco;. 鍥磋鎴戜滑@1point 3 acres
import java.io.FileReader;
import java.util.*;

public class Solution2 {
    public List<String> getTopKWords(String path, int k) throws Exception{
        List<String> result = new ArrayList<String>();
        if(k <= 0). 1point3acres.com/bbs
            return result;
        Scanner doc = new Scanner(new FileReader(path));
        HashMap<String, Integer> wordCnt = new HashMap<String, Integer>();
        while(doc.hasNextLine()){ // find the total number of occurrences for each word
            String line = doc.nextLine();
            String[] words = line.split("\\s+");
            for(String word : words){
                   if(wordCnt.containsKey(word)){. more info on 1point3acres.com
                       wordCnt.put(word, wordCnt.get(word)+1);
                   } else {
                       wordCnt.put(word, 1);
                   }. 1point 3acres 璁哄潧
                }
        }
        doc.close();. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴
-google 1point3acres
        Set<Map.Entry<String, Integer>> set = wordCnt.entrySet();
        List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(set); 鏉ユ簮涓浜.涓夊垎鍦拌鍧.
        Collections.sort(list, new Comparator<Map.Entry<String, Integer>>(){
            @Override
            public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2){
                return o2.getValue()-o1.getValue(); // from the highest occurrences to the lowest occurrences. Waral 鍗氬鏈夋洿澶氭枃绔,
            }
        });. Waral 鍗氬鏈夋洿澶氭枃绔,
        
        int upperbound = Math.min(k, list.size());. 1point3acres.com/bbs
        for(int i=0; i<upperbound; i++){// if k is larger than the number of words, then return all words
            result.add(list.get(i).getKey());
        }
        
        return result;
    }. more info on 1point3acres.com
. 鍥磋鎴戜滑@1point 3 acres
}


最后还剩8分钟,拷贝粘贴扔给我一道大题,关于字符串编码解码的,题目文字描述其中还有一堆乱码;他说这题你还能用java来做?我跟他确认题目意思都用了8分钟;最后说我可以面试完后做了发给他(好吧,他拿到了java版本的答案,真精明) 为了方便大家看,我剔除乱码,整理如下:
Where Did Those Numbers Come From?
In both modes, the program maintains a linked list of words that have appeared in the input. In compression mode, the program reads the next word from the input file and searches for it in the list. If it is not found, the program writes the word to the output file and inserts it at the front of the list. If the word is found in the i-th position in the list, the program writes out i, removes the word from the list, then reinserts it at the front (this is the move-to-front feature). For example, let us consider the text:
LOVE,   LOVE   ME   DO!      YOU   KNOW   I   LOVE   YOU,   YOU,   YOU.. visit 1point3acres.com for more.
which after compression becomes     
LOVE,   1   ME   DO!      YOU   KNOW   I   6   4,   1,   1.
Notice that LOVE is replaced by both 1 and 6, and that 1 replaces both LOVE and YOU. This is due to word insertions in the list and the effect of move-to-front. After the second LOVE is processed, the word list is simply
(LOVE)
hence the second instance of LOVE is replaced by the number 1. After the I is processed, the word list is. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴
(I, KNOW, YOU, DO, ME, LOVE)
Next, the third instance of LOVE is processed, the word is found in the 6th position (thus it is
replaced by number 6), and the list becomes:
(LOVE, I, KNOW, YOU, DO, ME)
When the second YOU is processed, YOU is found in the 4th position, and the list becomes:
(YOU, LOVE, I, KNOW, DO, ME)
Finally, when the last two instances of YOU are processed, the word is found in the first position.. 1point 3acres 璁哄潧
In decompression mode, a word read from input is written out again and inserted at the front of the list. When the number i is read, the word in the i-th position is written out, then the word is deleted from the list and reinserted at the front. Decompression ends when the number 0 is read. The decompressed version should be identical to the original in every respect! (In Unix, you can use the utility diff to check this.). 1point 3acres 璁哄潧
. 1point 3acres 璁哄潧

package cisco;. from: 1point3acres.com/bbs

import java.util.*;. from: 1point3acres.com/bbs

. 鍥磋鎴戜滑@1point 3 acres//the requirement does not specify "LOVE" or "love" is the same word, so I assume words are all in uppercase
public class MoveToFrontCoding {
    public String compression(String str) {
        LinkedList<String> list = new LinkedList<>();
        StringBuilder ret = new StringBuilder();
        int last = 0;
        for (int i = 0; i < str.length(); i++) {
            if (Character.toUpperCase(str.charAt(i)) >= 'A' && Character.toUpperCase(str.charAt(i)) <= 'Z') {
鏉ユ簮涓浜.涓夊垎鍦拌鍧.                 continue;
            } else {
                if (last != i) {. 鍥磋鎴戜滑@1point 3 acres
                    String s = str.substring(last, i);
                    int idx = list.indexOf(s);. 1point 3acres 璁哄潧
                    if (idx >= 0) {// if the word already exists, replace it with a number. From 1point 3acres bbs
                        list.remove(idx);
                        ret.append(idx + 1);
                    } else {// if the word does not exist, keep it
                        ret.append(s);
                    }
                    list.offerFirst(s);//insert the word at the beginning
                }
                last = i + 1;
                ret.append(str.charAt(i));//insert the word at the beginning
            }. From 1point 3acres bbs
        }-google 1point3acres
        if (last != str.length()) {
            String s = str.substring(last, str.length());
            int idx = list.indexOf(s);
            if (idx >= 0) {// if the word already exists, replace it with a number
                list.remove(idx);
                ret.append(idx + 1);
            } else {// if the word does not exist, keep it
                ret.append(s);
            }
            list.offerFirst(s);//insert the word at the beginning
        }
. 鍥磋鎴戜滑@1point 3 acres        return ret.toString();
    }. 1point 3acres 璁哄潧

    public String decompression(String str) {
        LinkedList<String> list = new LinkedList<>();. 1point3acres.com/bbs
        StringBuilder ret = new StringBuilder();
        int last = 0;. from: 1point3acres.com/bbs
        for (int i = 0; i < str.length(); i++) {
            if ((str.charAt(i) >= '0' && str.charAt(i) <= '9') || (Character.toUpperCase(str.charAt(i)) >= 'A' && Character.toUpperCase(str.charAt(i)) <= 'Z')) {
                continue;. more info on 1point3acres.com
            } else {
                if (last != i) {
                    String ss = str.substring(last, i);
                    if (ss.matches("\\d+")) {//  the word already exists, replace the index with the word
                        int idx = Integer.parseInt(ss) - 1;.1point3acres缃
                        ret.append(list.get(idx));
                        String s = list.remove(idx);
                        list.offerFirst(s);//insert the word at the beginning. From 1point 3acres bbs
                    } else {
                        ret.append(ss);
-google 1point3acres                        list.offerFirst(ss);//insert the word at the beginning
                    }. more info on 1point3acres.com
                }
                last = i + 1;
                ret.append(str.charAt(i));. Waral 鍗氬鏈夋洿澶氭枃绔,
            }. Waral 鍗氬鏈夋洿澶氭枃绔,
        }
        if (last != str.length()) {
            String ss = str.substring(last, str.length());
            if (ss.matches("\\d+")) {//  the word already exists, replace the index with the word-google 1point3acres
                int idx = Integer.parseInt(ss) - 1;
                ret.append(list.get(idx));
                String s = list.remove(idx);
                list.offerFirst(s);//insert the word at the beginning
            } else {
                ret.append(ss);
                list.offerFirst(ss);//insert the word at the beginning
            }
        }
        return ret.toString();
    }. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴

    public static void main(String[] args) {
        MoveToFrontCoding s = new MoveToFrontCoding();. From 1point 3acres bbs
        String originalStr = "LOVE, LOVE ME DO!!  YOU KNOW I LOVE YOU, YOU, YOU.";
        System.out.println("original string: ");
        System.out.println(originalStr);
        System.out.println("Compressing...");
        String s1 = s.compression(originalStr);
        System.out.println(s1);
        System.out.println("Decompressing...");
        String s2 = s.decompression(s1);
        System.out.println(s2);
    }
}



Result:.鏈枃鍘熷垱鑷1point3acres璁哄潧
. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴

original string:
LOVE, LOVE ME DO!!  YOU KNOW I LOVE YOU, YOU, YOU.
Compressing...-google 1point3acres
LOVE, 1 ME DO!!  YOU KNOW I 6 4, 1, 1.
Decompressing...
LOVE, LOVE ME DO!!  YOU KNOW I LOVE YOU, YOU, YOU.

3  这个印度人完全问我的项目经历

4. 这个印度人问完我的项目经历,让我用两种方法做string reverse,并且分析每一步的复杂度

A fox jumped over the fence
.1point3acres缃
package cisco;

public class Solution3 {
       public String reverseStr1(String input){
            String s = input.trim();
            int len = s.length();
            if(len == 0)
                return input;//the input only contains space, return it
            String[] arrStr = input.split("\\s+");  // compute O(n)  memory read O(n)  write O(n). visit 1point3acres.com for more.
            StringBuilder sb = new StringBuilder();
            for(int i=arrStr.length-1; i>=0; i--){  // compute O(n)  memory read O(n)  write O(n)
                sb.append(arrStr[i]+" ");        
            }
            String result = new String(sb); //compute O(n)  read O(n)  write O(n)
            result = result.trim();// remove the last empty space  compute O(n) read O(n)  write O(1)
            return result;
       }
       .1point3acres缃
        public String reverseStr2(String input) {
            String s = input.trim();
            int len = s.length();
            if(len == 0)
                return input;//the input only contains space, return it. Waral 鍗氬鏈夋洿澶氭枃绔,
            char[] cArr = s.toCharArray();
            for(int i=0; i<len/2; i++){// reverse the whole string  compute O(n)  memory read O(n)  write O(n)
                char tmp = cArr[i];
                cArr[i] = cArr[len-1-i];
                cArr[len-1-i] = tmp;. 鍥磋鎴戜滑@1point 3 acres
            }. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴
            . 1point 3acres 璁哄潧
            int m=0;
            for(int i=0; i<=len; i++){
                /* reverse each substring delimited by space
                 * compute O(n)  memory read O(n)  write O(n)*/. 涓浜-涓夊垎-鍦帮紝鐙鍙戝竷
                if(i==len || cArr[i]==' '){. Waral 鍗氬鏈夋洿澶氭枃绔,
                    int len1 = i-m;
                    for(int j=0; j<len1/2; j++){
                        char tmp1 = cArr[m+j]; 鏉ユ簮涓浜.涓夊垎鍦拌鍧.
                        cArr[m+j] = cArr[len1+m-1-j];
                        cArr[len1+m-1-j] = tmp1;.鏈枃鍘熷垱鑷1point3acres璁哄潧
                    }
                    m = i+1;
                }
            }
            
            return String.valueOf(cArr);
        }      
}


.鏈枃鍘熷垱鑷1point3acres璁哄潧现在感觉我完全在给印度人提供面试题答案了;还是分享给大家比较好. visit 1point3acres.com for more.

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八和九生 发表于 2016-7-2 14:55:55 | 显示全部楼层
关注一亩三分地公众号:
Warald_一亩三分地
我勒个去,这是new grad吗?感觉好难啊。。。
楼主好厉害= =
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八和九生 发表于 2016-7-2 15:02:04 | 显示全部楼层
关注一亩三分地微博:
Warald
八和九生 发表于 2016-7-2 14:55
我勒个去,这是new grad吗?感觉好难啊。。。
楼主好厉害= =

楼主的top k words写的好棒啊= = 学习了。。。
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lajiwushi 发表于 2016-7-6 07:04:21 | 显示全部楼层
谢谢楼主的分享!!!
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yingchal 发表于 2016-9-30 12:20:46 | 显示全部楼层
谢谢楼主分享,第一题题干真的好长啊
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