[Leetcode] Longest Consecutive Sequence

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.

For example,
Given [100, 4, 200, 1, 3, 2],
The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4.

Your algorithm should run in O(n) complexity.

使用容器实现。已经判断过的不用再次判断。

class Solution {
public:
    int longestConsecutive(vector<int> &num) {
        map<int, int> mp;
        for (int i = 0; i < num.size(); ++i) {
            mp[num[i]] = 1;
        }
        int len = 0, tmp;
        for (int i = 0; i < num.size(); ++i) {
            tmp = 1;
            if (mp[num[i]] == 1) {
                int left = num[i] - 1;
                while (mp.count(left) && mp[left] == 1) {
                    mp[left--] = 0;
                    ++tmp;
                }
                int right = num[i] + 1;
                while (mp.count(right) && mp[right] == 1) {
                    mp[right++] = 0;
                    ++tmp;
                }
                len = (len > tmp) ? len : tmp;
            }
        }
        return len;
    }
};