659. Split Array into Consecutive Subsequences

You are given an integer array sorted in ascending order (may contain duplicates), you need to split them into several subsequences, where each subsequences consist of at least 3 consecutive integers. Return whether you can make such a split.

Example 1:

Input: [1,2,3,3,4,5]
Output: True
Explanation:
You can split them into two consecutive subsequences : 
1, 2, 3
3, 4, 5

 Example 2:

Input: [1,2,3,3,4,4,5,5]
Output: True
Explanation:
You can split them into two consecutive subsequences : 
1, 2, 3, 4, 5
3, 4, 5

 Example 3:

Input: [1,2,3,4,4,5]
Output: False

 Note:

  1. The length of the input is in range of [1, 10000]

含义：给定一个升序的数组，要求拆分出多个子数组，子数组至少要有3个元素，且是公差为1的递增序列

 1     public boolean isPossible(int[] nums) {
 2         Map<Integer, Integer> cards = new HashMap<>();
 3         for (int i : nums) cards.put(i, cards.getOrDefault(i, 0) + 1);
 4         Map<Integer, Integer> map = new HashMap<>(); //key是已有的满足规则队列的下一个期待的数，value是满足规则的队列数，大于0才表示队列有效
 5         for (int i : nums) {
 6             if (cards.get(i) == 0) continue; // 这个数用完了
 7             if (map.getOrDefault(i, 0) > 0) {
 8                 // 加到已经有的队列
 9                 map.put(i, map.get(i) - 1);
10                 map.put(i + 1, map.getOrDefault(i + 1, 0) + 1);
11             } else if (cards.getOrDefault(i + 1, 0) > 0 && cards.getOrDefault(i + 2, 0) > 0) {
12                 // 取i，i+1，i+2这三个数，加到新的队列
13                 cards.put(i + 1, cards.get(i + 1) - 1);
14                 cards.put(i + 2, cards.get(i + 2) - 1);
15                 map.put(i + 3, map.getOrDefault(i + 3, 0) + 1);
16             } else return false; // 这个数无处容身
17             cards.put(i, cards.get(i) - 1);
18         }
19         return true;      
20     }

 

posted @ 2017-10-25 16:26  daniel456  阅读(169)  评论(0)  编辑  收藏  举报