LeetCode:Generate Parentheses

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回溯。

这题做得比较愉快，半个小时就通过了。

import java.util.ArrayList;import java.util.Arrays;import java.util.List;public class Solution {public List<String> generateParenthesis(int n) {List<String> result = new ArrayList<String>();if (n <= 0) {return result;}        int leftCount = 0;        int availableLeftCount = 0;        char[] solution = new char[n * 2];        Arrays.fill(solution, '-');        int i = 0;        while (i >= 0) {        if (solution[i] == '-') {        //try left        if (leftCount < n) {        solution[i] = '(';                leftCount++;        availableLeftCount++;        i++;        } else {        solution[i] = ')';//put a right                availableLeftCount--;        i++;        }        } else if (solution[i] == '(') {        //remove the '('        leftCount--;        availableLeftCount--;                if (availableLeftCount > 0) { //put a ')'        solution[i] = ')';                availableLeftCount--;        i++;        } else { //back        solution[i] = '-';        i--;        }        } else if (solution[i] == ')') {        //remove the ')'        availableLeftCount++;        solution[i] = '-';    i--;        }                if (i == n * 2) { //get a solution        String s = new String(solution);        //System.out.println(s);        result.add(s);                i--;        }        }                return result;    }public static void main(String[] args) {Solution s = new Solution();s.generateParenthesis(4);}}

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