leetcode--22--產生有效括號
阿新 • • 發佈:2019-01-27
原題: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:
[
"((()))",
"(()())",
"(())()",
"()(())",
"()()()"
]
解答:
C++版本
void search(int left, int right, string path, vector<string>& v) { if(!left && !right) { v.push_back(path); return ; } if(left > 0) search(left-1, right, path+"(", v); if(left < right) search(left, right-1, path+")", v); } vector<string> generateParenthesis(int n) { vector<string> v; search(n, n, "", v); return v; }
Java版本
<span style="font-size:24px;">private void helper(List<String> res, String present, int left, int right) { if (right == 0) { res.add(present); } if (left > 0) { helper(res, present + "(", left - 1, right); } if (right > left) { helper(res, present + ")", left, right - 1); } } public List<String> generateParenthesis(int n) { List<String> res = new ArrayList<String>(); if (n == 0) { return res; } helper(res, "", n, n); return res; }</span>
思路:
使用遞迴的方式產生括號
( -> (( 和 ()
(( -> (((和(()
() -> ()( 不能產生())
((( -> ((((和((()
(() -> (())和(()(
()( -> ()()和()((
... ...