Split Array into Consecutive Subsequences问题及解法

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问题描述：

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.

示例:

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

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

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

Note:

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

问题分析：

参考大神的博客：https://www.cnblogs.com/pk28/p/7384602.html

对于任何一个数，要么它能添加进现在有的分割中去，要么它能形成新的分割，如果两种情况都不满足，那么该数组不能形成有效的分割。

过程详见代码：

class Solution {
public:bool isPossible(vector<int>& nums) {int n = nums.size();if (n < 3) return false;unordered_map<int, int> mp, mp2;for (int i = 0; i < n; ++i) mp[nums[i]]++;for (int i = 0; i < n; i++){int x = nums[i];if (mp[x] <= 0) continue;if (mp2[x - 1] > 0)mp[x]--, mp2[x - 1]--, mp2[x]++;else if (mp[x + 1] >0 && mp[x + 2] > 0){mp[x]--, mp[x + 1]--, mp[x + 2]--;mp2[x + 2]++;}else return false;}return true;}
};

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