php基础查找算法

1、顺序查找

function line_search($array,$tar)
{
    if(!is_array($array) || count($array) < 1) return false;
    for($i=0;$i<count($array);$i++){
        if($array[$i] == $tar){
            return $i;
        }
    }
    return false;
}

line_search($arr,34);

2、二分法查找

// 非递归
function binary_search($array,$tar)
{
    if(!is_array($array) || count($array) < 1) return false;
        // 数组必须排序
    sort($array);
    $high = count($array) - 1;
    $low = 0;
    while($low <= $high){
        $middle = intval(($high + $low) / 2);
        if($array[$middle] > $tar){
            $high = $middle - 1;
        }elseif($array[$middle] < $tar){
            $low = $middle + 1;
        }else{
            return $middle; 
        }
    }
    return false;
}

binary_search($arr,165.4);

// 递归
function binary_search($array,$tar,$high=0,$low=0)
{
    if(!is_array($array) || count($array) < 1) return false;
    sort($array);
    if($low <= $high){
        $middle = intval(($high + $low) / 2);
        if($array[$middle] > $tar){
            $high = $middle - 1;
            echo $high."</br>";
            return binary_search($array,$tar,$high,$low);
        }elseif($array[$middle] < $tar){
            $low = $middle + 1;
            return binary_search($array,$tar,$high,$low);
        }else{
            return $middle; 
        }
    }
    return false;
}

binary_search($arr,125,count($arr),0);