A thunder interview question: Find the number of times each letter appears in a string, the question string

Source: Internet
Author: User

A thunder interview question: Find the number of times each letter appears in a string, the question string
By Long Luo

Personal blog address

Last time inThunderDuring the interview, I encountered an algorithm question:

There is a long and long string, all composed of uppercase letters. You must find the number of times each letter appears in this string. Methods in STL are not allowed.

When I got this question, I first thought of the following methods:

In fact, it is relatively simple to review this question later, but unfortunately, it was not answered within the specified time, resulting in failure to pass the interview and get an Offer, record this question here.

Answer this question again.

How?

In fact, this question has a very simple solution to prevent, create an array, the size is 26, each character in the string is'A'The result is that each letter is in the array.Element Base ValueThe last array we get is the number of times each letter appears in this string.

Based on the above analysis, you can write the following code:

Package com. algorithm. alphabetSort;/*** there is a long string, which contains some letters. Calculate the number of occurrences of each letter (case sensitive ). ** @ Author luolong * @ date: 00:54:17 **/public class AlphabetSort {private static String str = "empty"; private static int [] outArray = new int [26]; public static void main (String [] args) {AlphabetSortString (str); printSortArray (outArray);} public static void AlphabetSortString (String str) {char cTemp; for (int I = 0; I <str. length (); I ++) {cTemp = str. charAt (I); outArray [cTemp-'a'] ++ ;}} private static void printSortArray (int [] arr) {for (int I = 0; I <arr. length; I ++) {char c = (char) ('A' + I); System. out. print ("" + c + "=" + arr [I] + "");}}}
Extension and extension 1

If a string is not only a capital letter, but a capital letter, how should it be written?

It is actually quite simple, as shown below:

If (cTemp> = 'A' & cTemp <= 'Z') {/*** uppercase letter */outArray [cTemp-'a'] ++ ;} else if (cTemp> = 'A' & cTemp <= 'Z ') {/*** lowercase letter */outArray [cTemp-'A' + 26] ++;} else {}
Extension and Extension 2

If the string isAll charactersAre statistics required?

What should we do?

Later, I found that it is also possible to store with HashMap, and this problem can be solved perfectly. The Code is as follows:

Package com. algorithm. alphabetSort; import java. util. arrayList; import java. util. collections; import java. util. hashMap; import java. util. list; import java. util. map;/*** there is a long string containing some letters. Calculate the number of occurrences of each letter (case sensitive ). ** @ Author luolong * @ date: 01:03:38 **/public class CharSort {private static String str = "empty"; public static void main (String args []) {Map <Character, KeyValue> map = new HashMap <Character, KeyValue> (); char c; KeyValue kv = null; for (int I = 0; I <str. length (); I ++) {c = str. charAt (I); kv = map. get (c); if (kv = null) {kv = new KeyValue (); kv. ch = c; kv. count = 1; map. put (c, kv);} else {kv. count ++ ;}list <KeyValue> List = new ArrayList <KeyValue> (map. values (); Collections. sort (list); for (KeyValue o: list) {System. out. print (o. ch + "=" + o. count + "") ;}} class KeyValue implements Comparable {public int compareTo (Object obj) {if (obj instanceof KeyValue) {KeyValue kv = (KeyValue) obj; return kv. count-this. count;} return-1;} char ch; int count ;}

Above.

If you have other better methods, please join us :-)

Created by Long Luo at 01:08:20 @ Shenzhen, China. Completed By Long Luo at 01:28:39 @ Shenzhen, China.

Related Article

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.