jodd.util.BinarySearchBase Maven / Gradle / Ivy
// Copyright (c) 2003-present, Jodd Team (http://jodd.org)
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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package jodd.util;
/**
* Abstract binary search. It is more abstract then {@link jodd.util.BinarySearch}.
*/
public abstract class BinarySearchBase {
/**
* Compares element at index position with the target.
*/
protected abstract int compare(int index);
// ---------------------------------------------------------------- find
/**
* Finds index of given element in inclusive index range. Returns negative
* value if element is not found.
*/
public int find(int low, int high) {
while (low <= high) {
int mid = (low + high) >>> 1;
int delta = compare(mid);
if (delta < 0) {
low = mid + 1;
} else if (delta > 0) {
high = mid - 1;
} else {
return mid;
}
}
// not found
return -(low + 1);
}
// ---------------------------------------------------------------- first
/**
* Finds very first index of given element in inclusive index range. Returns negative
* value if element is not found.
*/
public int findFirst(int low, int high) {
int ndx = -1;
while (low <= high) {
int mid = (low + high) >>> 1;
int delta = compare(mid);
if (delta < 0) {
low = mid + 1;
} else {
if (delta == 0) {
ndx = mid;
}
high = mid - 1;
}
}
if (ndx == -1) {
return -(low + 1);
}
return ndx;
}
// ---------------------------------------------------------------- last
/**
* Finds very last index of given element in inclusive index range. Returns negative
* value if element is not found.
*/
public int findLast(int low, int high) {
int ndx = -1;
while (low <= high) {
int mid = (low + high) >>> 1;
int delta = compare(mid);
if (delta > 0) {
high = mid - 1;
} else {
if (delta == 0) {
ndx = mid;
}
low = mid + 1;
}
}
if (ndx == -1) {
return -(low + 1);
}
return ndx;
}
}