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Java Exercises: Check a string follows a specified pattern

Java Basic: Exercise-199 with Solution

Write a Java program to check a string follows a given pattern.

Example pattern:
Given pattern = "xyyx", str = "red black black red", return true.
Given pattern = "xyyx", str = "red black black green", return false.
Given pattern = "xxxx", str = "red black black red", return false.
Given pattern = "xxxx", str = "red red red red", return true.

Sample Solution:

Java Code:

import java.util.*;
public class Solution {
 public static void main(String[] args) {
  String str = "red black black red";
  //String str = "red red red red"; 
  String pattern = "xyxx";
  //String pattern = "xxxx";
  System.out.print("Is the string and pattern matched? " + word_Pattern_Match(pattern, str));
 }

 public static boolean word_Pattern_Match(String pattern, String str) {
  char[] word_pattern = pattern.toCharArray();
  String[] words = str.split(" ");

  Map < Character, String > map = new HashMap < > ();
  Set < String > set = new HashSet < > ();

  for (int i = 0; i < word_pattern.length; i++) {
   if (map.containsKey(word_pattern[i])) {
    if (!map.get(word_pattern[i]).equals(words[i])) {
     return false;
    }
    continue;
   }

   if (set.contains(words[i])) {
    return false;
   }
   map.put(word_pattern[i], words[i]);
   set.add(words[i]);
  }
  return true;
 }
}

Sample Output:

Is the string and pattern matched? false

Pictorial Presentation:

Java exercises: Check a string follows a specified pattern
Java exercises: Check a string follows a specified pattern
Java exercises: Check a string follows a specified pattern
Java exercises: Check a string follows a specified pattern

Flowchart:

Flowchart: Java exercises: Check a string follows a specified pattern

Java Code Editor:

Company:  Uber Dropbox

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Java: Tips of the Day

How to remove leading zeros from alphanumeric text?

Regex is the best tool for the job; what it should be depends on the problem specification. The following removes leading zeroes, but leaves one if necessary (i.e. it wouldn't just turn "0" to a blank string).

s.replaceFirst("^0+(?!$)", "")

The ^ anchor will make sure that the 0+ being matched is at the beginning of the input. The (?!$) negative lookahead ensures that not the entire string will be matched.

Test harness:

String[] in = {
    "01234",         // "[1234]"
    "0001234a",      // "[1234a]"
    "101234",        // "[101234]"
    "000002829839",  // "[2829839]"
    "0",             // "[0]"
    "0000000",       // "[0]"
    "0000009",       // "[9]"
    "000000z",       // "[z]"
    "000000.z",      // "[.z]"
};
for (String s : in) {
    System.out.println("[" + s.replaceFirst("^0+(?!$)", "") + "]");
}

Ref: https://bit.ly/2Qdcl8a