<?php public function select_two_part($a,$n,$target){ $l = 0; $r = $n-1; $mid = 0; while($l<=$r){ $mid = round(l+r)/2; //round(l+(r-l)/2);这个可以避免Int型越界,在强类型语言中会遇到 if($target = $arr[$mid]) { return $mid; } if($target>$mid){ $l = $mid+1; }else{ $r = $mid-1; } } return -1;//没有找到返回-1 }
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