LeetCode——Generate Parentheses

Generate Parentheses

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:

"((()))", "(()())", "(())()", "()(())", "()()()"

Java代码：

public class Solution {    public List<String> generateParenthesis(int n) {        List list = new ArrayList<String>();List list_2 = new ArrayList<String>();String str = new String();str = "";if (n == 0)return null;if (n == 1) {list.add("()");return list;}list_2 = generateParenthesis(n - 1);Iterator ite = list_2.iterator();while (ite.hasNext()) {str = (String) ite.next();list.add("(" + str + ")");list.add("()"+str);list.add(str+"()");}list.remove(list.size() - 1);return list;    }}

Submission Result: Wrong Answer

Input:4Output:["(((())))","()((()))","((()))()","(()(()))","()()(())","()(())()","((())())","()(())()","(())()()","((()()))","()(()())","(()())()","(()()())","()()()()"]Expected:["(((())))","((()()))","((())())","((()))()","(()(()))","(()()())","(()())()","(())(())","(())()()","()((()))","()(()())","()(())()","()()(())","()()()()"]

 。。。测试了一下发现和list中排列顺序还有关系。。题目也没说

Java代码；

public class Solution {    public List<String> generateParenthesis(int n) {        List list = new ArrayList<String>();List list_2 = new ArrayList<String>();String str = new String();str = "";if (n == 0)return null;if (n == 1) {list.add("()");return list;}list_2 = generateParenthesis(n - 1);Iterator ite = list_2.iterator();while (ite.hasNext()) {str = (String) ite.next();list.add("(" + str + ")");// list.add("()"+str);// list.add(str+"()");}ite = list_2.iterator();while (ite.hasNext()) {str = (String) ite.next();// list.add("("+str+")");// list.add("()" + str);list.add(str + "()");}ite = list_2.iterator();while (ite.hasNext()) {str = (String) ite.next();// list.add("("+str+")");list.add("()" + str);// list.add(str + "()");}list.remove(list.size() - 1);return list;    }}

Submission Result: Wrong Answer

Input:4Output:["(((())))","((()()))","((())())","(()()())","(()(()))","((()))()","(()())()","(())()()","()()()()","()(())()","()((()))","()(()())","()(())()","()()()()"]Expected:["(((())))","((()()))","((())())","((()))()","(()(()))","(()()())","(()())()","(())(())","(())()()","()((()))","()(()())","()(())()","()()(())","()()()()"]

我是服了这个排序的逻辑了

Java代码：

public class Solution {   public ArrayList<String> generateParenthesis(int n) {        ArrayList<String> res = new ArrayList<String>();        if (n <= 0)            return res;        StringBuilder sb = new StringBuilder();        generate(n, n, sb, res);        return res;    }     private void generate(int l, int r, StringBuilder sb, ArrayList<String> res) {        if (r < l)            return;        if (l == 0 && r == 0) {            res.add(sb.toString());        }        if (l > 0) {            sb.append("(");            generate(l - 1, r, sb, res);            sb.deleteCharAt(sb.length() - 1);        }        if (r > 0) {            sb.append(")");            generate(l, r - 1, sb, res);            sb.deleteCharAt(sb.length() - 1);        }    }}

网上找了一个答案，才发现解题思路和我完全不一样。。。怪不得测试集合里的排序这么奇葩