Java LowerBound
/**
* <html>
* <body>
* <P> Copyright 1994-2018 JasonInternational </p>
* <p> All rights reserved.</p>
* <p> Created on 2018年4月10日 上午9:46:32</p>
* <p> Created by Jason</p>
* </body>
* </html>
*/
package cn.ucaner.algorithm.search;
/**
* Lower bound search algorithm.<br>
* Lower bound is kind of binary search algorithm but:<br>
* -If searched element doesn't exist function returns index of first element which is bigger than searched value.<br>
* -If searched element is bigger than any array element function returns first index after last element.<br>
* -If searched element is lower than any array element function returns index of first element.<br>
* -If there are many values equals searched value function returns first occurrence.<br>
* Behaviour for unsorted arrays is unspecified.
* <p>
* Complexity O(log n).
* <p>
* @author Bartlomiej Drozd <mail@bartlomiejdrozd.pl>
* @author Justin Wetherell <phishman3579@gmail.com>
*/
public class LowerBound {
private LowerBound() { }
public static int lowerBound(int[] array, int length, int value) {
int low = 0;
int high = length;
while (low < high) {
final int mid = (low + high) / 2;
if (value <= array[mid]) {
high = mid;
} else {
low = mid + 1;
}
}
return low;
}
}