Create ValidParentheses.java

Author: techieJarek

ValidParentheses.java

@@ -0,0 +1,42 @@
+import com.sun.org.apache.xalan.internal.xsltc.compiler.util.StringStack;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Stack;
+
+/**
+ * Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
+ *
+ * An input string is valid if:
+ *
+ * Open brackets must be closed by the same type of brackets.
+ * Open brackets must be closed in the correct order.
+ * Note that an empty string is also considered valid.
+ */
+public class ValidParentheses {
+
+    public static void main(String[] args){
+        String s1 = "{{({})}}";
+        String s2 = "{([)]}";
+        System.out.println("String s1 is valid = " + isValid(s1));
+        System.out.println("String s2 is valid = " + isValid(s2));
+    }
+
+    private static boolean isValid(String s) {
+        Stack<Character> openingCharsStack = new StringStack();
+        Map<Character, Character> matchingParentheses = new HashMap();
+        matchingParentheses.put('{', '}');
+        matchingParentheses.put('(', ')');
+        matchingParentheses.put('[', ']');
+        for(char c : s.toCharArray()){
+            if(matchingParentheses.containsKey(c)) {
+                openingCharsStack.push(c);
+            }
+            else if((openingCharsStack.isEmpty() && matchingParentheses.containsValue(c))
+                    || (!openingCharsStack.isEmpty() && matchingParentheses.get(openingCharsStack.pop()) != c)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}