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binary.php
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191 lines (173 loc) · 4.63 KB
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<?php
/**
* 找到第一个=value的元素
* @param array $numbers
*
* @return void
* @date 2018/11/27
* @author yuanliandu <yuanliandu@qq.com>
*/
function findFirstEqual(array $numbers,$find) {
$length = count($numbers);
$low = 0;
$high = $length - 1;
while($low <= $high) {
$mid = $low + (($high-$low)>>1);
if($numbers[$mid] > $find) {
$high = $mid - 1;
}else if($numbers[$mid] < $find) {
$low = $mid + 1;
}else {
/**
* 如果是第一个元素，或之前一个元素不等于我们要找的值
* 我们就找到了第一个=find的element
*/
if($mid==0 || $numbers[$mid-1]!=$find) {
return $mid;
}else {
$high = $mid - 1;
}
}
}
return -1;
}
/**
* 找到最后一个=find的元素
* @param array $numbers
* @param [type] $find
*
* @return void
* @date 2018/11/27
* @author yuanliandu <yuanliandu@qq.com>
*/
function findLastEqual(array $numbers,$find) {
$length = count($numbers);
$low = 0;
$high = $length - 1;
while($low <= $high) {
$mid = $low + (($high-$low)>>1);
if($numbers[$mid] > $find) {
$high = $mid - 1;
}else if($numbers[$mid] < $find) {
$low = $mid + 1;
}else {
/**
* 如果mid是最后一个元素的index
* 或mid后一个元素!=我们要找的值
* 则找到了最后一个=find的value
*/
if($mid==$length-1 || $numbers[$mid+1]!=$find) {
return $mid;
}else {
$low = $mid + 1;
}
}
}
return -1;
}
/**
* 找到第一个大于等于find的元素
* @param array $numbers
* @param [type] $find
*
* @return void
* @date 2018/11/27
* @author yuanliandu <yuanliandu@qq.com>
*/
function findFirstGreaterEqual(array $numbers,$find) {
$length = count($numbers);
$low = 0;
$high = $length - 1;
while($low <= $high) {
$mid = $low + (($high-$low)>>1);
if($numbers[$mid] >= $find) {
if ($mid == 0 || $numbers[$mid-1] < $find) {
return $mid;
}else {
$high = $mid - 1;
}
}else {
$low = $mid + 1;
}
}
return -1;
}
/**
* 找到最后一个小于等于find的元素
* @param array $numbers
* @param [type] $find
*
* @return void
* @date 2018/11/27
* @author yuanliandu <yuanliandu@qq.com>
*/
function findLastLessEqual(array $numbers,$find) {
$length = count($numbers);
$low = 0;
$high = $length - 1;
while($low <= $high) {
$mid = $low + (($high-$low)>>1);
if($numbers[$mid] <= $find) {
if($mid==$length-1 || $numbers[$mid+1]> $find) {
return $mid;
}
$low = $mid + 1;
}else {
$high = $mid - 1;
}
}
return -1;
}
/**
* 循环数组中找指定元素
* @param array $numbers
* @param [type] $find
*
* @return void
* @date 2018/11/27
* @author yuanliandu <yuanliandu@qq.com>
*/
function searchCircularArray(array $numbers,$find) {
$length = count($numbers);
$low = 0;
$high = $length - 1;
while($low <= $high) {
$mid = $low + (($high-$low)>>1);
if($numbers[$mid] === $find) {
return $mid;
}
if($numbers[$low] > $numbers[$mid]) {
// 后半部分是有序数组
if(($numbers[$mid] < $find) && ($numbers[$high] >= $find)) {
if($numbers[$high] === $find) return $high;
//在后半个区间内
$low = $mid + 1;
}else {
$high = $mid - 1;
}
}else {
// 前半部分是有序的
if(($numbers[$low] <= $find) && ($numbers[$mid] > $find)) {
// 在有序区间内
if($numbers[$low] === $find) return $low;
$high = $mid - 1;
}else {
$low = $mid + 1;
}
}
}
return -1;
}
/***
* 测试
*/
$numbers = [1,2,3,3,3,4,5,6,8,11,13];
$find = 3;
var_dump(findFirstEqual($numbers,$find));//找到第一个等于find的元素
var_dump(findFirstGreaterEqual($numbers,$find));//找到第一个大于等于find的元素
var_dump(findLastEqual($numbers,$find));//找到最后一个=find的元素
var_dump(findLastLessEqual($numbers,$find));//找到最后一个小于等于find的元素
//测试在循环数组中找到指定数字
$numbers = [9,10,1,2,3,4,5,6,7,8];
$find = 2;
var_dump(searchCircularArray($numbers,$find));