add a solution for 32

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_32.java

@@ -23,4 +23,50 @@ public int longestValidParentheses(String s) {
             return result;
         }
     }
+
+    public static class Solution2 {
+        /**
+         * my lengthy but original solution on 4/5/2021, the idea is to convert the valid parenthesis pairs into numbers and push them onto a stack.
+         */
+        public int longestValidParentheses(String s) {
+            Stack<String> stack = new Stack<>();
+            int longest = 0;
+            for (char c : s.toCharArray()) {
+                if (c == '(') {
+                    stack.push(c + "");
+                } else {
+                    if (stack.isEmpty()) {
+                        continue;
+                    } else {
+                        if (stack.peek().equals("(")) {
+                            stack.pop();
+                            stack.push("2");
+                        } else {
+                            int sum = 0;
+                            while (!stack.isEmpty() && !stack.peek().equals("(")) {
+                                sum += Integer.parseInt(stack.pop());
+                            }
+                            if (!stack.isEmpty()) {
+                                stack.pop();//pop off the open paren
+                                sum += 2;
+                                stack.push("" + sum);
+                            }
+                            longest = Math.max(longest, sum);
+                        }
+                    }
+                }
+            }
+            int result = 0;
+            while (!stack.isEmpty()) {
+                if (stack.peek().equals("(")) {
+                    stack.pop();
+                    result = 0;
+                } else {
+                    result += Integer.parseInt(stack.pop());
+                    longest = Math.max(result, longest);
+                }
+            }
+            return longest;
+        }
+    }
 }

src/test/java/com/fishercoder/_32Test.java

@@ -8,14 +8,60 @@
 
 public class _32Test {
     private static _32.Solution1 solution1;
+    private static _32.Solution2 solution2;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _32.Solution1();
+        solution2 = new _32.Solution2();
     }
 
     @Test
     public void test1() {
         assertEquals(2, solution1.longestValidParentheses("(()"));
+        assertEquals(2, solution2.longestValidParentheses("(()"));
     }
+
+    @Test
+    public void test2() {
+        assertEquals(2, solution1.longestValidParentheses("()(()"));
+        assertEquals(2, solution2.longestValidParentheses("()(()"));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals(4, solution1.longestValidParentheses("(())("));
+        assertEquals(4, solution2.longestValidParentheses("(())("));
+    }
+
+    @Test
+    public void test4() {
+        assertEquals(6, solution1.longestValidParentheses("()(())"));
+        assertEquals(6, solution2.longestValidParentheses("()(())"));
+    }
+
+    @Test
+    public void test5() {
+        assertEquals(4, solution1.longestValidParentheses(")()())"));
+        assertEquals(4, solution2.longestValidParentheses(")()())"));
+    }
+
+    @Test
+    public void test6() {
+        assertEquals(4, solution1.longestValidParentheses(")()())()()("));
+        assertEquals(4, solution2.longestValidParentheses(")()())()()("));
+    }
+
+    @Test
+    public void test7() {
+        assertEquals(8, solution1.longestValidParentheses("((())())"));
+        assertEquals(8, solution2.longestValidParentheses("((())())"));
+    }
+
+    @Test
+    public void test8() {
+        assertEquals(10, solution1.longestValidParentheses(")()(((())))("));
+        assertEquals(10, solution2.longestValidParentheses(")()(((())))("));
+    }
+
 }