Salesforce笔记

1. Java inheritance

2. Two Sum

3. 各种sort以及他们的runtime

4. Implement merge sort

5. Stack和Queue的运用

6. Find duplicate: 

Leetcode #83: Remove Duplicates from Sorted List -> 如果有多余的，只保留其中一个即可

    public ListNode deleteDuplicates(ListNode head) {
        ListNode current = head;
        while(current != null){
            while(current.next != null && current.val == current.next.val){
                current.next = current.next.next;
            }
            current = current.next;
        }
        return head;
    }

 

Leetcode #82: Remove Duplicates from Sorted List II -> 如果有多余的，所有有关于这个element的node都要删掉

    public ListNode deleteDuplicates(ListNode head) {
        ListNode fake = new ListNode(-1);
        fake.next = head;
        ListNode pre = fake;
        ListNode cur = head;
        while(cur != null){
            while(cur.next != null && cur.val == cur.next.val){
                cur = cur.next;
            }
            if(pre.next == cur){
                pre = pre.next;
            }else{
                pre.next = cur.next;
                cur = cur.next;
            }
        }
        return fake.next;
    }

 

7. Leetcode #33: Search in Rotated Sorted Array

    public int search(int[] nums, int target) {
        int l = 0, r = nums.length - 1, m = (l + r)/2, result = -1;
        while(l <= r){
            m = (l + r) / 2;
            if(nums[m] == target){
                result = m;
                break;
            }else if(l == r){
                break;
            }
            if((nums[m] <= nums[r] && target > nums[m] && target <= nums[r]) || 
              (nums[l] <= nums[m] && (target > nums[m] || target < nums[l]))){
                l = m + 1;
            }else{
                r = m;
            }
        }
        return result;
    }

8. Leetcode #15: 3Sum

    public List> threeSum(int[] nums) {
        List> result = new ArrayList<>();
        if(nums.length < 3){
            return result;
        }
        Arrays.sort(nums);
        if(nums[0] > 0 || nums[nums.length-1] < 0){
            return result;
        }

        for(int i = 0; i < nums.length - 2; i++){
            if(i == 0 || nums[i - 1] != nums[i]){
                int j = i + 1; 
                int k = nums.length - 1;
                while(j < k){
                    if(nums[i] == - (nums[j] + nums[k])){
                        List current = new ArrayList<>();
                        current.add(nums[i]);
                        current.add(nums[j]);
                        current.add(nums[k]);
                        result.add(current);
                    
                        // check repeated values
                        while(j < k && nums[j] == nums[j + 1]){
                            j++;
                        }
                        while(j < k && nums[k] == nums[k - 1]){
                            k--;
                        }
                        j++;
                        k--;
                    }else if(nums[i] < - (nums[j] + nums[k])){   
                        // nums[j] + nums[k] can be larger
                        j++;
                    }else{
                        k--;
                    }
                }
            }
            
        }
        return result;
    }

 

转载于:https://www.cnblogs.com/yxcindy/p/10026702.html