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119 lines (89 loc) · 2.83 KB
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package com.binarySearch;
public class RBS {
public static void main(String[] args) {
int[] arr = {4,5,6,7,0,1,2};
System.out.println(search(arr, 3));
}
static int search(int[] arr, int target){
int pivot = findPivot(arr);
if( pivot == -1){
return binarySearch(arr, target, 0, arr.length - 1);
}
if( arr[pivot] == target){
return pivot;
}
if ( target >= arr[0]){
return binarySearch(arr, target, 0, pivot - 1);
}
return binarySearch(arr, target, pivot + 1, arr.length - 1);
}
static int findPivot(int[] arr){
int start = 0;
int end = arr.length - 1;
while(start <= end){
int mid = start + (end - start)/2;
if(mid < end && arr[mid] > arr[mid+1] ){
return mid;
}
if(mid > start && arr[mid] < arr[mid-1] ){
return mid-1;
}
if( arr[start] >= arr[mid] ){
end = mid - 1;
}else{
start = mid + 1;
}
}
return -1;
}
static int findPivotWithDuplicates(int[] arr){
int start = 0;
int end = arr.length - 1;
while(start <= end){
int mid = start + (end - start)/2;
if(mid < end && arr[mid] > arr[mid+1] ){
return mid;
}
if(mid > start && arr[mid] < arr[mid-1] ){
return mid-1;
}
// if elements at middle, start, end are equal then just skip the duplicates
if( arr[mid] == arr[start] && arr[mid] == arr[end] ){
// Skip the duplicates
// NOTE: what if these elements at start and end were the pivot??
// check if start is pivot
if(arr[start] > arr[start + 1]){
return start;
}
start ++;
if(arr[end] < arr[end - 1]){
return end - 1;
}
end --;
}else if(arr[start] < arr[mid] || (arr[start] == arr[mid] && arr[end] < arr[mid])){
start = mid + 1;
}else{
end = mid - 1;
}
}
return -1;
}
static int binarySearch(int [] arr, int target, int start, int end){
// while start is not greater than end
while(start <= end){
// better way to find the mid
int mid = start + (end - start) / 2;
// target is greater than mid
if(target > arr[mid]){
start = mid + 1;
}
else if(target < arr[mid]){
end = mid - 1;
}
else{
return mid;
}
}
return -1;
}
}