GenerateParentheses
GenerateParentheses.java 源码
package algorithm.backtracking.leetcode;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
/**
* @author roseduan
* @time 2020/10/27 12:33 下午
* @description 括号生成
*/
public class GenerateParentheses {
/**
* 深度优先搜索的思路解决
*/
public List<String> generateParenthesis1(int n) {
List<String> res = new ArrayList<>();
dfs(n, 0, 0, "", res);
return res;
}
private void dfs(int n, int left, int right, String cur, List<String> res) {
if (cur.length() == 2 * n) {
res.add(cur);
return;
}
if (left < n) {
dfs(n, left + 1, right, cur + "(", res);
}
if (right < left) {
dfs(n, left, right + 1, cur + ")", res);
}
}
/**
* 广度优先的思路解决
*/
public List<String> generateParenthesis2(int n) {
List<String> res = new ArrayList<>();
Queue<Node> queue = new LinkedList<>();
queue.add(new Node(n, n, ""));
while (!queue.isEmpty()) {
Node node = queue.poll();
if (node.left == 0 && node.right == 0) {
res.add(node.cur);
}
if (node.left > 0) {
queue.add(new Node(node.left - 1, node.right, node.cur + "("));
}
if (node.right > 0 && node.right > node.left) {
queue.add(new Node(node.left, node.right - 1, node.cur + ")"));
}
}
return res;
}
static class Node {
int left;
int right;
String cur;
public Node(int left, int right, String cur) {
this.left = left;
this.right = right;
this.cur = cur;
}
}
}
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