?1.最長連續序列

128. 最長連續序列

給定一個未排序的整數數組?nums?，找出數字連續的最長序列（不要求序列元素在原數組中連續）的長度。

請你設計并實現時間復雜度為?O(n)?的算法解決此問題。

示例 1：

輸入：nums = [100,4,200,1,3,2]
輸出：4
解釋：最長數字連續序列是 [1, 2, 3, 4]。它的長度為 4。

示例 2：

輸入：nums = [0,3,7,2,5,8,4,6,0,1]
輸出：9

示例 3：

輸入：nums = [1,0,1,2]
輸出：3

提示：

• 0 <= nums.length <= 105
• -109 <= nums[i] <= 109

public static void main(String[] args) {int[] nums1 = {100,4,200,1,3,2};//排序int[] nums2 = {0};//1個數int[] nums3 = {0,-1};//絕對值==1 連續int[] nums = {0,3,7,2,5,8,4,6,0,1};//去重int longestConsecutive = longestConsecutive2(nums);System.out.println(longestConsecutive);}//1-answerpublic static int longestConsecutive2(int[] nums) {if(nums.length == 0){return 0;}Arrays.sort(nums);//排序int longestStreak = 1;//最大連續長度int currentStreak = 1;//當前連續長度for(int i = 1; i < nums.length; i++){if(nums[i] != nums[i-1]){//去重if(nums[i] == nums[i-1] + 1){//差值1，連續currentStreak += 1;}else{longestStreak = Math.max(longestStreak, currentStreak);//判斷更新currentStreak = 1;//重置}}}return Math.max(longestStreak, currentStreak);}//1-mypublic static int longestConsecutive(int[] nums) {Arrays.sort(nums);int longest = 0;List<List<Integer>> enterList = new ArrayList<>();//起始，長度for (int i = 0;i<nums.length; i++){List<Integer> list = new ArrayList<>();list.add(nums[i]);int left = 0;int right = 0;for (int j = i+1; j<nums.length ;j++){left = nums[j-1];right = nums[j];if (left==right){continue;}if ( Math.abs(left-right) == 1){list.add(nums[j]);}if (Math.abs(left-right) != 1){break;}}enterList.add(list);i = i+list.size()-1;}for (List<Integer> o : enterList) {//空間利用率很差if (o.size()>longest){longest = o.size();}}return longest;}

2.移動零

283. 移動零

給定一個數組?nums，編寫一個函數將所有?0?移動到數組的末尾，同時保持非零元素的相對順序。

請注意?，必須在不復制數組的情況下原地對數組進行操作。

示例 1:

輸入: nums = [0,1,0,3,12]
輸出: [1,3,12,0,0]

示例 2:

輸入: nums = [0]
輸出: [0]

提示:

• 1 <= nums.length <= 104
• -231?<= nums[i] <= 231?- 1

進階：你能盡量減少完成的操作次數嗎？

public static void main(String[] args) {int[] nums = {0,3,7,2,5,8,4,6,0,1};//去重moveZeroes2(nums);System.out.println(Arrays.toString(nums));}//2-answerpublic static void moveZeroes2(int[] nums) {int i=0,j=0;while(j<nums.length){if(nums[j] != 0){nums[i] = nums[j];i++;//indexAfterMove}j++;//index}while(i < nums.length){nums[i++] = 0;}}//2-mypublic static void moveZeroes(int[] nums) {int zeroCount = 0;Map<Integer,Integer> rightIndexAndNumMap = new HashMap<>();for (int i = 0; i < nums.length; i++) {if (nums[i] == 0){zeroCount++;}if (nums[i]!=0 && zeroCount>0){//開始移動rightIndexAndNumMap.put(i-zeroCount,nums[i]);}}for (Map.Entry<Integer, Integer> entry : rightIndexAndNumMap.entrySet()) {nums[entry.getKey()] = entry.getValue();}for (int i = 0; i < zeroCount; i++) {nums[nums.length-i-1] = 0;}}