php循环练习题

1.通过for循环将数组中值求和、求平均值

<?php
    $num=[1,2,3,4,5,6,7,8,9];
    $sum = 0;
    for ($i=0,$n=count($num); $i < $n ; $i++) {
        $sum += $num[$i];
    }
    echo '和是: ' .$sum,'<br>';
    echo '平均值: '.number_format($sum/count($num),1);
 ?>

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2.数组翻转

<?php
    $stu=['wang','li','zhang','sun','jiang','liu','xu'];
    for ($i=0, $j=count($stu)-1; $i < $j; $i++, $j--) {
        [$stu[$i],$stu[$j]] = [$stu[$j],$stu[$i]];
    }
    print_r($stu);
 ?>

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3.遍历二维数组

<?php
    $stu=[
        [1,2,3,4],
        ['a', 'b', 'c', 'd']
    ];
    for ($i=0; $i < count($stu); $i++) {
        for ($j=0; $j < count($stu[$i]); $j++) {
            echo $stu[$i][$j],'&nbsp';
        }
    }
 ?>

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4.打印水仙花数

<?php
    for ($i=100; $i <= 999; $i++) {
        $a = (int)($i/100);
        $b = (int)(($i%100)/10);
        $c = $i % 10;
        if ($i == pow($a,3) + pow($b,3) +  pow($c,3)) {
            echo $i,'<br>';
        }
    }
 ?>

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5.打印100以内的斐波那契数（迭代法）

<?php
    $num1 = 1;
    $num2 = 1;
    echo $num1,'&nbsp;',$num2,'&nbsp';
    while (true) {
        $num3 = $num1 + $num2;
        if ($num3 > 100) {
            break;
        }
        echo $num3,'&nbsp';
        $num1 = $num2;
        $num2 = $num3;
    }
 ?>