Example
Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P I N
A L S I G
Y A H R
P I
时间复杂度: O(N)- 空间复杂度: O(N)
print_r(test("PAYPALISHIRING",3));
function test($str,$num) {
if ($num==1||$num>=mb_strlen($str)) {
return $str;
}
$arr = [];
$index = 0;
$step = 1;
for ($i = 0; $i < mb_strlen($str); $i++) {
$arr[$index][] = $str[$i];
if ($index == 0) {
//代表往下走
$step = 1;
} elseif ($index == $num - 1) {
//代表往上走
$step = -1;
}
$index += $step;
}
$endArr = [];
foreach ($arr as $ar) {
$endArr[] = implode('',$ar);
}
return implode('', $endArr);
}
