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