Php algorithm-- catching water droplets

php algorithm-- catching water droplets

A novice PHP programmer, who has been on the job for half a year and is still hovering in endless additions, deletions, modifications and data optimization, has recently been brought into the algorithm pit by the front-end brother and has done a lot of algorithm problems.
this question comes from the collar buckle network, which is more interesting.
given a matrix of m x n, in which the values are all positive integers, representing the height of each cell in the two-dimensional height map, please calculate the maximum volume of Rain Water in the figure.

description:

m an dna re integers less than 110. The height of each unit is greater than 0 and less than 20000.

example:

the height map of 3x6 is given as follows:
[
[1 br > [1 br 4],
[3 br 2],
[3 br >]

[3, 2, 3, 3, 2, 1]

]

[3, 2, 3, 3, 2, 1]

returns 4.

[[1,4,3,1,3,2],[3,2,1,3,2,4],[2,3,3,2,3,1]]

after it rains, Rain Water will be stored in these squares. The total amount of rain water received is 4.

my idea is:
the volume that can receive water is the volume of each layer that is vacant, but some of the volume of the vacancy is notched. So the specific idea:

1.
2.
3. = -
4.

I don"t know if there is a better idea.

public function water(){ $arr = [ [1,4,3,1,3,2], [3,2,1,3,2,4], [2,3,3,2,3,1] ]; $shui = 0; // //$max $b = []; foreach($arr as $key=>$value){ $a=$arr[$key]; $b = array_merge($a,$b); sort($b); } $max = $b[count($b)-1]; for($i=0;$i<=$max-1;$iPP){ $eacharr = []; // foreach($arr as $key =>$row){ foreach($row as $key1=>$row1){ if($row1-$i<0){ $row1 =0; }else{ $row1 = $row1-$i; } $eacharr[$key][$key1] = $row1; } } // $shui += $this->each($eacharr); } return $shui; } /** * * @param [array] $arr [] * @return [int] [] */ public function each($arr){ $shui = 0; // foreach ($arr as $i => $row) { foreach($row as $j =>$row1){ //$w 0 $w = $arr[$i][$j]; if($w==0){ // if( $i==0||$j == 0||$i == count($arr)-1||$j == count($row)-1){ $arr[$i][$j] = 'kou'; // $arr = $this->kou($arr,$i,$j); } } } } //shu foreach ($arr as $i => $row) { foreach($row as $j =>$row1){ $w = $arr[$i][$j]; if($w===0){ $shuiPP; } } } return $shui; } /** * * @param [array] $arr [] * @param integer $i [] * @param integer $j [] * @return [array] $arr [] */ public function kou($arr,$i,$j){ if(isset($arr[$i+1][$j])&&$arr[$i+1][$j]===0){ $arr[$i+1][$j] = 'kou'; $arr = $this->kou($arr,$i+1,$j); }elseif(isset($arr[$i-1][$j])&&$arr[$i-1][$j]===0){ $arr[$i-1][$j] = 'kou'; $arr = $this->kou($arr,$i-1,$j); }elseif(isset($arr[$i][$j+1])&&$arr[$i][$j+1]===0){ $arr[$i][$j+1] = 'kou'; $arr = $this->kou($arr,$i,$j+1); }elseif(isset($arr[$i][$j-1])&&$arr[$i][$j-1]===0){ $arr[$i][$j-1] = 'kou'; $arr = $this->kou($arr,$i,$j-1); }else{ return $arr; } return $arr; }