g0001_0100.s0022_generate_parentheses.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0001_0100.s0022_generate_parentheses;

// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #String #Dynamic_Programming
// #Backtracking #2022_02_17_Time_1_ms_(87.91%)_Space_43.6_MB_(19.97%)

import java.util.ArrayList;
import java.util.List;

public class Solution {
    public List generateParenthesis(int n) {
        StringBuilder sb = new StringBuilder();
        List ans = new ArrayList<>();
        return generate(sb, ans, n, n);
    }

    private List generate(StringBuilder sb, List str, int open, int close) {
        if (open == 0 && close == 0) {
            str.add(sb.toString());
            return str;
        }
        if (open > 0) {
            sb.append('(');
            generate(sb, str, open - 1, close);
            sb.deleteCharAt(sb.length() - 1);
        }
        if (close > 0 && open < close) {
            sb.append(')');
            generate(sb, str, open, close - 1);
            sb.deleteCharAt(sb.length() - 1);
        }
        return str;
    }
}