[数据结构与算法]算法打卡，用于自律

题目一?

?解法

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode node = new ListNode(-1);
        ListNode ans = node;
        int carry = 0;
        while (l1 != null || l2 != null) {
            int n1 = l1 != null ? l1.val : 0;
            int n2 = l2 != null ? l2.val : 0;
            int sum = n1+n2+carry;
            carry = 0;
            node.next = new ListNode(sum%10);
            node = node.next;
            if(sum/10>=1){
                carry = 1;
            }
            if(l1!=null){
                l1 = l1.next;
            }
            if(l2!=null){
                l2 = l2.next;
            }
        }
        if(carry>=1){
            node.next = new ListNode(1);
        }
        return ans.next;
    }
}

第二题

?解法

class Solution {
    public int lengthOfLongestSubstring(String s) {
        Set<Character> occ = new HashSet<Character>();
        int rk = -1, ans = 0;
        for(int i = 0;i<s.length();i++){
            if (i != 0) {
                occ.remove(s.charAt(i - 1));
            }
            while(rk+1<s.length()&&!occ.contains(s.charAt(rk + 1))){
                occ.add(s.charAt(rk + 1));
                ++rk;
            }
            ans = Math.max(ans, rk - i + 1);
        }
        return ans;
    }
}

第三题

?解法

class Solution {
    public int sumOfUnique(int[] nums) {
        int sum = 0;
        int[] arr = new int[101];
        for(int i = 0;i<nums.length;i++){
            arr[nums[i]]+=1;
        }
        for(int i = 0;i<arr.length;i++){
            if(arr[i]==1){
                sum+=i;
            }
        }
        return sum;
    }
}

第四题

?解法

class Solution {
    public int maxAscendingSum(int[] nums) {
        if(nums.length==1) return nums[0];
        int sum = nums[0];
        int max = Integer.MIN_VALUE;
        for(int i =1;i<nums.length;i++){
            if(nums[i]>nums[i-1]){
                sum +=nums[i];
                max = Math.max(max,sum);
            }else{
                max = Math.max(max,sum);
                sum = nums[i];
            }
        }
        return max;
    }
}