Update README.md

Author: pony

README.md

@@ -182,6 +182,7 @@ phpunit -vvv
 |`0018. 四数之和`|[4Sum](https://leetcode.com/problems/4sum/)|[Solution](https://github.com/imajinyun/leetcode-php/blob/master/src/leetcode/FourSum.php)|
 |`0287. 寻找重复数`|[Find the Duplicate Number](https://leetcode.com/problems/find-the-duplicate-number/)|[Solution](https://github.com/imajinyun/leetcode-php/blob/master/src/leetcode/FourSum.php)|
 |`0844. 比较含退格的字符串`|[Backspace String Compare](https://leetcode.com/problems/backspace-string-compare/)|[Solution](https://github.com/imajinyun/leetcode-php/blob/master/src/leetcode/BackspaceStringCompare.php)|
+|`0997. 有序数组的平方`|[Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array/)|[Solution](https://github.com/imajinyun/leetcode-php/blob/master/src/leetcode/SquaresOfASortedArray.php)|
 
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