**Leetcode 659. Split Array into Consecutive Subsequences

Posted 2022-12-10 Z-Pilgrim

https://leetcode.com/problems/split-array-into-consecutive-subsequences/description/

这个代码 技巧性太强了 参考了http://www.cnblogs.com/grandyang/p/7525821.html

基本思路就是，up维护数可能存在次数的上限，

class Solution 
public:
    bool isPossible(vector<int>& nums) 
        unordered_map< int, int > freq, up;
        for (auto v : nums) freq[v]++;
        for (auto v : nums) 
            if (!freq[v])continue;
            if ( up[v] > 0 ) 
                up[v] --;
                up[v+1]++;
             else if ( freq[v + 1] > 0 && freq[v + 2] > 0 ) 
                freq[v+1]--;
                freq[v+2]--;
                up[v+3] ++;
             else return false;
            freq[v]--;
        
        return true;
    
;