22. Generate Parentheses

coderbean · coderbean · commit f66916f6d1d9 · 2019-03-08T18:56:21.000+08:00
diff --git a/src/leetcode/_20_/Main.java b/src/leetcode/_20_/Main.java
@@ -6,7 +6,7 @@
 public class Main {
     public static void main(String[] args) {
         Solution solution = new Solution();
-        System.out.println(solution.isValid("["));
+        System.out.println(solution.isValid("((()()))()"));
     }
 }
 
diff --git a/src/leetcode/_22_/Main.java b/src/leetcode/_22_/Main.java
@@ -0,0 +1,13 @@
+package leetcode._22_;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println( solution.generateParenthesis(4));
+        System.out.println( solution.generateParenthesis(4).size());
+    }
+}
+
diff --git a/src/leetcode/_22_/Solution.java b/src/leetcode/_22_/Solution.java
@@ -0,0 +1,28 @@
+package leetcode._22_;
+
+import java.util.ArrayList;
+import java.util.List;
+
+class Solution {
+    public List<String> generateParenthesis(int n) {
+        List<String> result = new ArrayList<>();
+        traceBack(result, "", n, n);
+        return result;
+    }
+
+    private void traceBack(List<String> result, String curStr, int left, int rigth) {
+        if (left == 0 && rigth == 0) {
+            result.add(curStr);
+            return;
+        }
+        if (left > rigth) { // 如果 剩余的 右括号比比左括号 少，说明 当前 str 的右括号多，无法匹配，不再递归
+            return;
+        }
+        if (left >= 0) {
+            traceBack(result, curStr + '(', left - 1, rigth);
+        }
+        if (rigth >= 0) {
+            traceBack(result, curStr + ')', left, rigth - 1);
+        }
+    }
+}
diff --git a/src/leetcode/_22_/solution.md b/src/leetcode/_22_/solution.md
@@ -0,0 +1,50 @@
+### [22\. Generate Parentheses](https://leetcode.com/problems/generate-parentheses/)
+
+Difficulty: **Medium**
+
+
+Given _n_ pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
+
+For example, given _n_ = 3, a solution set is:
+
+```
+[
+  "((()))",
+  "(()())",
+  "(())()",
+  "()(())",
+  "()()()"
+]
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public List<String> generateParenthesis(int n) {
+        List<String> result = new ArrayList<>();
+        traceBack(result, "", n, n);
+        return result;
+    }
+​
+    private void traceBack(List<String> result, String curStr, int left, int rigth) {
+        if (left == 0 && rigth == 0) {
+            result.add(curStr);
+            return;
+        }
+        if (left > rigth) { // 如果 剩余的 右括号比比左括号 少，说明 当前 str 的右括号多，无法匹配，不再递归
+            return;
+        }
+        if (left >= 0) {
+            traceBack(result, curStr + '(', left - 1, rigth);
+        }
+        if (rigth >= 0) {
+            traceBack(result, curStr + ')', left, rigth - 1);
+        }
+    }
+}
+        if (rigth >= 0) {
+```
diff --git a/src/leetcode/_23_/Main.java b/src/leetcode/_23_/Main.java
@@ -0,0 +1,15 @@
+package leetcode._23_;
+
+import leetcode.common.ListNode;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        ListNode node = new ListNode(1).setNext(new ListNode(2).setNext(new ListNode(3)).setNext(new ListNode(4)));
+        System.out.println(solution.swapPairs(node));
+    }
+}
+
diff --git a/src/leetcode/_23_/Solution.java b/src/leetcode/_23_/Solution.java
@@ -0,0 +1,17 @@
+package leetcode._23_;
+
+import leetcode.common.ListNode;
+
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public ListNode swapPairs(ListNode head) {
+        return null;
+    }
+}
diff --git a/src/leetcode/_23_/solution.md b/src/leetcode/_23_/solution.md

Original file line number	Diff line number	Diff line change
`@@ -6,7 +6,7 @@`
`6`	`6`	`public class Main {`
`7`	`7`	`public static void main(String[] args) {`
`8`	`8`	`Solution solution = new Solution();`
`9`		`- System.out.println(solution.isValid("["));`
	`9`	`+ System.out.println(solution.isValid("((()()))()"));`
`10`	`10`	`}`
`11`	`11`	`}`
`12`	`12`