added Valid Parentheses Problem in String Problems

AyushJoshi2001 · web-flow · commit faefda7c6319 · 2021-10-01T14:13:29.000+05:30
diff --git a/Topic/String.md b/Topic/String.md
@@ -14,3 +14,4 @@
 
 * [Roman to Integer](https://leetcode.com/problems/roman-to-integer/), [Solution](Solution/romanToInt.java) 
 
+* [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/), [Solution](Solution/validParentheses.java) 

Original file line number	Diff line number	Diff line change
`@@ -14,3 +14,4 @@`
`14`	`14`
`15`	`15`	`* [Roman to Integer](https://leetcode.com/problems/roman-to-integer/), [Solution](Solution/romanToInt.java)`
`16`	`16`
	`17`	`+* [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/), [Solution](Solution/validParentheses.java)`