最长连续序列（dp）

题目：https://leetcode-cn.com/problems/longest-consecutive-sequence/ 代码：https://leetcode-cn.com/problems/longest-consecutive-sequence/solution/c-dong-tai-gui-hua-fu-za-du-on-by-izeuwy/

class Solution {
public:
    int longestConsecutive(vector& nums) {
        unordered_map dp;
        int ret = 0;
        for(auto &x : nums) {
            if(!dp[x]) dp[x - dp[x - 1]] = dp[x + dp[x + 1]] = dp[x] = dp[x - 1] + dp[x + 1] + 1;
            ret = max(ret, dp[x]);
        }
        return ret;
    }
};