PHP面试——基本算法

一、排序

1、冒泡

//冒泡

$arr = array(2,4,654,76,43,23,65,786,43,12);

function mySort($arr){
	for($i = 0;$i $arr[$j+1]){
				$t = $arr[$j];
				$arr[$j] = $arr[$j+1];
				$arr[$j+1] = $t;
			}
		}
	}
	return $arr;
}
var_dump(mySort($arr));

2、快排

//快排

$arr = array(2,4,654,76,43,23,65,786,43,12);
function mySort($arr){
	if(count($arr) <= 1){
		return $arr;
	}
	$left = $right = array();
	for($i = 1;$i  $arr[0]){
			$right[] = $arr[$i];
		}else{
			$left[] = $arr[$i];
		}
	}
	$left = mySort($left);
	$right = mySort($right);
	return array_merge($left,array($arr[0]),$right);
}
var_dump(mySort($arr));

3、插入

//插入
//
$arr = array(2,4,654,76,43,23,65,786,43,12);

function mySort($arr){
	for($i = 1;$i < count($arr);$i++){
		for($j = $i;$j > 0;$j--){
			if($arr[$j] < $arr[$j-1]){
				$t = $arr[$j];
				$arr[$j] = $arr[$j-1];
				$arr[$j-1] = $t;
			}else{
				break;
			}
		}
	}
	return $arr;
}
var_dump(mySort($arr));

4、二维数组排序

//二维数组根据指定字段排序(asc)


 $arr = array(
            0=>array('id'=>8,'name'=>'Tom'),
            1=>array('id'=>9,'name'=>'Peter'),
            2=>array('id'=>5,'name'=>'Jack')
   		);
 function mySort($arr,$sort_key,$sort_order=SORT_ASC,$sort_type=SORT_NUMERIC){
 	$arrs = array();
 	if(is_array($arr) || is_array($arrs)){
 		foreach($arr as $key => $value){
 			$arrs[] = $value[$sort_key];
 		}
 		array_multisort($arrs,$sort_order,$sort_type,$arr);
 		return $arr;
 	}
 }
 var_dump(mySort($arr,'id'));

二、查找

1、顺序（必须考虑效率）

//顺序查找

$arr = array(1,2,3,4,5,6,7,8,9,12,14,15,16);

function search($arr,$key){
	$n = count($arr);
	$arr[$n] = $key;
	for($i = 0;$i < $n;$i++){
		if($arr[$i] == $key){
			break;
		}
	}
	if($i < $n){
		return $i;
	}else{
		return -1;
	}
}
var_dump(search($arr,12));

2、二分

//二分查找

$arr = array(1,2,3,4,5,6,7,8,9,12,14,15,16);
$low = 0;
$high = count($arr)-1;
$key = 12;
function search($arr,$low,$high,$key){
	while($low <= $high){
		$mid = intval(($low+$high)/2);
		if($arr[$mid] == $key){
			return $mid;
		}elseif($arr[$mid] < $key){
			$low = $mid +1;
		}elseif($arr[$mid] > $key){
			$high = $mid -1;
		}
	}
        return -1;
 }
var_dump(search($arr,$low,$high,$key));