leetcode-128-Longest Consecutive Sequence

#include <iostream>#include <vector>#include <unordered_set>using namespace std;/* 由于可能有负整数，所以用数组不太合适。 用hashmap，c++用unordered_set的接口， 保证时间复杂度为O(n)。 遍历一次nums里的元素，如果哈希表里面有的话就找到它的相邻元素 并把它删掉，避免下次重复重复计算。这样的话每次一找就找的是连续 一串数。 */class Solution {public:    int longestConsecutive(vector<int>& nums) {        unordered_set<int> myset;        for (int i = 0; i < nums.size(); i++) {            myset.insert(nums[i]);        }        int max = 0;        while (!myset.empty()) {            int start = *myset.begin();            int counter = 1;            myset.erase(start);            int left = start - 1, right = start + 1;            while (myset.find(left) != myset.end()) {                myset.erase(left);                counter++;                left--;            }            while (myset.find(right) != myset.end()) {                myset.erase(right);                counter++;                right++;            }            if (counter > max) {                max = counter;            }        }        return max;    }};int main(int argc, const char * argv[]) {    vector<int> myvec = {100, 4, 200, 1, 3, 2};    Solution s;    cout << s.longestConsecutive(myvec) << endl;    return 0;}