CODEWITHSUNDEEP
php
user3319461
user3319461

Reputation:

Matrix formation, there is something wrong in the loops

I am trying to get this kind of matrix:

1 0 0 0 5
0 2 0 4 0
0 0 3 0 0 
0 2 0 4 0
1 0 0 0 5

and here is the code:

$n = 5;
$flag = 0;

for($i=1; $i<=$n; $i++){
    for($j=1; $j<=$n; $j++){
        if($i == $j){
            echo "$i ";
        }else{
            echo "0 ";
        }

        if($j == $n - $flag){
            echo $n - $flag." ";
            $flag++;
        }

    }
    echo "</br>";
}

the output is:

1 0 0 0 0 5 
0 2 0 0 4 0 
0 0 3 3 0 0 
0 0 2 0 4 0 
0 1 0 0 0 5

there is something wrong in the middle. I think it is because two for loops overlap there. How to fix thiis?

Upvotes: 0

Views: 51

Answers (2)

user764357
user764357

Reputation:

The reason isn't an overlap in the loops. Its an overlap of the two if statements.

In the inner loop, you always print 6 things.

for($j=1; $j<=$n; $j++){
    if($i == $j){        // <--- This will always print in each iteraton (i.e 5 times)
        echo "$i ";
    }else{
        echo "0 ";
    }

    if($j == $n - $flag){   // <--- This will print once in the loop (the 6th extra)
        echo $n - $flag." ";
        $flag++;
    }

}

Since $j is equal to $flag, you don't need to keep track of it. Change it to this (Check it on ideone):

for($j=1; $j<=$n; $j++){
    if($i == $j){
        echo "$i ";
    } elseif($j == $n - $i + 1){
        echo $n - ($i-1)." ";
    } else {
        echo "0 ";
    }
}

Upvotes: 1

Abed Hawa
Abed Hawa

Reputation: 1362

Try this code to output the array you want:

$n = 6;

for($i=1; $i<$n; $i++){
    for($j=1; $j<$n; $j++){
        if($i == $j){
            echo "$i ";
        } else if ($j == $n - $i) {
            echo $n - $i ." ";
        } else {
            echo "0 ";
        }
    }
    echo "</br>";
}

Upvotes: 2

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