Java每日一练(20230401) 合并K个升序链表、最长有效括号、分割回文串

public class mergeKLists {
    public static class ListNode {
        int val;
        ListNode next;
        ListNode() {
        }
        ListNode(int val) {
            this.val = val;
        }
        ListNode(int val, ListNode next) {
            this.val = val;
            this.next = next;
        }
    }
    public static class Solution {
        public ListNode mergeKLists(ListNode[] lists) {
            if (lists == null || lists.length == 0)
                return null;
            return merge(lists, 0, lists.length - 1);
        }
        public ListNode merge(ListNode[] lists, int low, int high) {
            if (low == high)
                return lists[low];
            int mid = low + (high - low) / 2;
            ListNode l1 = merge(lists, low, mid);
            ListNode l2 = merge(lists, mid + 1, high);
            return mergeTwoLists(l1, l2);
        }
        public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
            ListNode dummy = new ListNode(-1);
            ListNode cur = dummy;
            while (l1 != null && l2 != null) {
                if (l1.val < l2.val) {
                    cur.next = l1;
                    l1 = l1.next;
                } else {
                    cur.next = l2;
                    l2 = l2.next;
                }
                cur = cur.next;
            }
            cur.next = l1 != null ? l1 : l2;
            return dummy.next;
        }
    }
    public static ListNode[] arraysToLists(int[][] nums) {
        ListNode[] lists = new ListNode[nums.length];
        for (int i = 0; i < nums.length; i++) {
            int[] arr = nums[i];
            ListNode head = new ListNode(0);
            ListNode cur = head;
            for (int num : arr) {
                cur.next = new ListNode(num);
                cur = cur.next;
            }
            lists[i] = head.next;
        }
        return lists;
    }
    public static void traverseList(ListNode head) {
        ListNode cur = head;
        int count = 0;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        System.out.print("[");
        for (cur = head; cur != null; cur = cur.next) {
            if (--count>0)
                System.out.print(cur.val + ",");
            else
                System.out.print(cur.val);
        }
        System.out.println("]");
    }
    public static void main(String[] args) {
        Solution s = new Solution();
        int[][] lists = {{1,4,5},{1,3,4},{2,6}};
        ListNode[] nodelists = arraysToLists(lists);
        traverseList(s.mergeKLists(nodelists));
    }
}

import java.util.*;
public class longestValidParentheses {
    public static class Solution {
        public int longestValidParentheses(String s) {
            int left = 0, right = 0, max = 0;
            for (int i = 0; i < s.length(); i++) {
                if (s.charAt(i) == '(')
                    left++;
                else
                    right++;
                if (left == right)
                    max = Math.max(max, left * 2);
                if (right > left)
                    left = right = 0;
            }
            left = 0;
            right = 0;
            for (int i = s.length() - 1; i >= 0; i--) {
                if (s.charAt(i) == '(')
                    left++;
                else
                    right++;
                if (left == right)
                    max = Math.max(max, left * 2);
                if (right < left)
                    left = right = 0;
            }
            return max;
        }
    }
    public static void main(String[] args) {
        Solution s = new Solution();
        System.out.println(s.longestValidParentheses("(()"));
        System.out.println(s.longestValidParentheses(")()()"));
        System.out.println(s.longestValidParentheses(""));
    }
}

import java.util.*;
public class partition {
    public static class Solution {
        public List<List<String>> partition(String s) {
            boolean[][] dp = new boolean[s.length()][s.length()];
            for (int len = 1; len <= s.length(); len++) {
                for (int i = 0; i <= s.length() - len; i++) {
                    if (len == 1)
                        dp[i][i] = true;
                    else if (s.charAt(i) == s.charAt(i + len - 1) && (len == 2 || dp[i + 1][i + len - 2])) {
                        dp[i][i + len - 1] = true;
                    }
                }
            }
            return solution(s, 0, dp);
        }
        public List<List<String>> solution(String s, int start, boolean[][] dp) {
            ArrayList<List<String>> list = new ArrayList<>();
            if (start == s.length()) {
                List<String> li = new ArrayList<>();
                list.add(li);
                return list;
            }
            for (int i = start; i < s.length(); i++) {
                if (dp[start][i]) {
                    String first = s.substring(start, i + 1);
                    for (List<String> li : solution(s, i + 1, dp)) {
                        li.add(0, first);
                        list.add(li);
                    }
                }
            }
            return list;
        }
    }
    public static void showStringLists(List<List<String>> lists){
        int size_lists = lists.size();
        System.out.print("[");
        for (List<String> innerList : lists) {
            int size_inner = innerList.size();
            System.out.print("[\"");
            for (String str : innerList) {
                System.out.print(str);
                if (--size_inner>0)
                    System.out.print("\",\"");
            }
            System.out.print("\"]");
            if (--size_lists>0)
                System.out.print(", ");
        }
        System.out.println("]");       
    }
    public static void main(String[] args) {
        Solution s = new Solution();
        showStringLists(s.partition("aab"));
    }
}