Initial data commit

Task/Balanced-brackets/Java/balanced-brackets-1.java

@@ -0,0 +1,49 @@
+public class BalancedBrackets {
+
+    public static boolean hasBalancedBrackets(String str) {
+        int brackets = 0;
+        for (char ch : str.toCharArray()) {
+            if (ch == '[') {
+                brackets++;
+            } else if (ch == ']') {
+                brackets--;
+            } else {
+                return false;   // non-bracket chars
+            }
+            if (brackets < 0) {   // closing bracket before opening bracket
+                return false;
+            }
+        }
+        return brackets == 0;
+    }
+
+    public static String generateBalancedBrackets(int n) {
+        assert n % 2 == 0;   // if n is odd we can't match brackets
+        char[] ans = new char[n];
+        int openBracketsLeft = n / 2;
+        int unclosed = 0;
+        for (int i = 0; i < n; i++) {
+            if (Math.random() >= 0.5 && openBracketsLeft > 0 || unclosed == 0) {
+                ans[i] = '[';
+                openBracketsLeft--;
+                unclosed++;
+            } else {
+                ans[i] = ']';
+                unclosed--;
+            }
+        }
+        return String.valueOf(ans);
+    }
+
+    public static void main(String[] args) {
+        for (int i = 0; i <= 16; i += 2) {
+            String brackets = generateBalancedBrackets(i);
+            System.out.println(brackets + ": " + hasBalancedBrackets(brackets));
+        }
+
+        String[] tests = {"", "[]", "][", "[][]", "][][", "[[][]]", "[]][[]"};
+        for (String test : tests) {
+            System.out.println(test + ": " + hasBalancedBrackets(test));
+        }
+    }
+}