JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: Find longest substring without repeating characters.


Description:

Given a string, find the longest substrings without repeating characters. Iterate through the given string, find the longest maximum substrings.


Code:
package com.java2novice.algos;

import java.util.HashSet;
import java.util.Set;

public class MyLongestSubstr {

	private Set<String> subStrList = new HashSet<String>();
	private int finalSubStrSize = 0;
	
	public Set<String> getLongestSubstr(String input){
		//reset instance variables
		subStrList.clear();
		finalSubStrSize = 0;
		// have a boolean flag on each character ascii value
		boolean[] flag = new boolean[256];
		int j = 0;
		char[] inputCharArr = input.toCharArray();
		for (int i = 0; i < inputCharArr.length; i++) {
			char c = inputCharArr[i];
			if (flag[c]) {
				extractSubString(inputCharArr,j,i);
				for (int k = j; k < i; k++) {
					if (inputCharArr[k] == c) {
						j = k + 1;
						break;
					}
					flag[inputCharArr[k]] = false;
				}	
			} else {
				flag[c] = true;
			}
		}
		extractSubString(inputCharArr,j,inputCharArr.length);
		return subStrList;
	}
	
	private String extractSubString(char[] inputArr, int start, int end){
		
		StringBuilder sb = new StringBuilder();
		for(int i=start;i<end;i++){
			sb.append(inputArr[i]);
		}
		String subStr = sb.toString();
		if(subStr.length() > finalSubStrSize){
			finalSubStrSize = subStr.length();
			subStrList.clear();
			subStrList.add(subStr);
		} else if(subStr.length() == finalSubStrSize){
			subStrList.add(subStr);
		}
		
		return sb.toString();
	}

	public static void main(String a[]){
		MyLongestSubstr mls = new MyLongestSubstr();
		System.out.println(mls.getLongestSubstr("java2novice"));
		System.out.println(mls.getLongestSubstr("java_language_is_sweet"));
		System.out.println(mls.getLongestSubstr("java_java_java_java"));
		System.out.println(mls.getLongestSubstr("abcabcbb"));
	}
}

Output:
[a2novice]
[uage_is]
[_jav, va_j]
[cab, abc, bca]
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  15. Write a program to find common elements between two arrays.
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  19. Write a program to check the given number is a prime number or not?
  20. Write a program to find the given number is Armstrong number or not?
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  29. Write a program to convert string to number without using Integer.parseInt() method.
  30. Write a program to find two lines with max characters in descending order.
  31. Write a program to find the sum of the first 1000 prime numbers.
  32. Find longest substring without repeating characters.
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Knowledge Centre
What is fail-fast in java?
A fail-fast system is nothing but immediately report any failure that is likely to lead to failure. When a problem occurs, a fail-fast system fails immediately. In Java, we can find this behavior with iterators. Incase, you have called iterator on a collection object, and another thread tries to modify the collection object, then concurrent modification exception will be thrown. This is called fail-fast.
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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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