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Find second largest element in an array

Find second largest element in an unsorted array. We can reach the solution in three ways. Solution 1 Sort the array and return last but one element. We could use already existing sorting methods in JDK Arrays class and sort the array. public static int findSecondLargestV1( int [] array ){ if ( array . length == 0 || array . length < 2){ return -1; } Arrays.sort( array ); return array [ array . length - 2]; } Complexity: Since this solution depends on sorting, the complexity is equal to complexity of sorting algorithm, ie., O(n log n) Solution 2 public static int findSecondLargestV2( int [] array ){ if ( array . length == 0 || array . length < 2){ return -1; } int max = -1; for ( int i = 0; i < array . length ; i ++){ if ( array [ i ] > max ){ max = array [ i ]; } } int secondMax = -1; for (

Merge two sorted Lists or Arrays

Code to merge two array lists: public static ArrayList<Integer> mergeLists(ArrayList<Integer> l1 , ArrayList<Integer> l2 ){ ArrayList<Integer> l3 = new ArrayList<Integer>(); int i = 0; int j = 0; while ( i < ( l1 .size()) && j < ( l2 .size())){ if ( l1 .get( i ) < l2 .get( j )){ l3 .add( l1 .get( i )); i ++; } else { l3 .add( l2 .get( j )); j ++; } } if ( i < l1 .size()){ while ( i < l1 .size()){ l3 .add( l1 .get( i )); i ++; } } else if ( j < l2 .size()){ while ( j < l2 .size()){ l3 .add( l2 .get( j )); j ++; } } return l3 ; } Code to merge two arrays: public static int[] mergeArrays(int[] a, int[] b){ if((a == null || a.length == 0) && (b == null || b.length == 0)) return new int[0]; if((a == null || a.length == 0)) return b; if(b == n

Binary search (recursive and non-recursive)

Recursive solution: public static int binarySearch( int [] array , int startIndex , int endIndex , int value ){ int midIndex = ( startIndex + endIndex )/2; if ( array [ midIndex ] == value ){ return value ; } if ( startIndex > endIndex ){ return -1; } if ( value < array [ midIndex ]){ int sI = startIndex ; int eI = midIndex - 1; return binarySearch( array , sI , eI , value ); } else { int sI = midIndex + 1; int eI = endIndex ; return binarySearch( array , sI , eI , value ); } } Non-Recursive solution: public static int binarySearchNoRecursion( int [] array , int value ){ int startIndex = 0; int endIndex = array . length - 1; while ( startIndex <= endIndex ){ int midIndex = ( startIndex + endIndex )/2; if ( array [ midIndex ] == value ){ return value ; } if ( value < ar

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