Binary Search

Array must be sorted first before searching.

example
Sorted array: L = [1, 3, 4, 6, 8, 9, 11]
   Target value: X = 4
   Compare X to 6. X is smaller. Repeat with L = [1, 3, 4].
   Compare X to 3. X is larger. Repeat with L = [4].
   Compare X to 4. X equals 4, so the position is returned.

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public class BinarySearch{ public static void main(String []args){ // Binary search must be sort first int[] array = new int[]{10,20,50,53,68,81,92,105,110,200,280,360,361,386,400}; if(binSearch(array,81) == -1) System.out.print("not found"); else System.out.print("found at index "+ binSearch(array,81)); } public static int binSearch(int[] arr, int search){ int first =0; int last = arr.length-1; int mid=0; while(first<=last){ mid = (first+last)/2; if(arr[mid] == search) return mid; else if (arr[mid]<search) first = mid+1; else last = mid-1; } return -1; } }

Longest Palindrome in String

Longest Palindromic substring. Given a string, find the longest substring which is palindrome. For example, if the given string is "forgeeksskeegfor", the output should be "geeksskeeg".

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public class PalinLong{ public static void main(String []args){ String s = "forgeeksskeegfor"; String longest=""; for(int x=0;x<s.length();x++){ for(int y=x+1;y<=s.length();y++){ String t = s.substring(x,y); if(isPalin(t)){ if(t.length()>longest.length()){ longest = t; } } } } System.out.print(longest); } public static boolean isPalin(String s){ String rev=""; for(int x=s.length()-1;x>=0;x--){ rev = rev + s.charAt(x); } if(rev.equals(s)) return true; else return false; } }