LeetCode 128 Longest Consecutive Sequence (C++, Python)

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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.
Solution C++


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class Solution {
public:
    int longestConsecutive(vector<int> &num) {
        unordered_set<int> graph;
        for (int i = 0; i < num.size(); ++i) {
            graph.insert(num[i]);    
        }
        int len = 0;
        while (!graph.empty()) {
            auto it = graph.begin();
            int tmplen = 1;
            auto less = graph.find(*it - 1);
            while (less != graph.end()) {
                tmplen ++;
                auto tmp = graph.find(*less - 1);
                graph.erase(less);
                less = tmp;
            }
            auto more = graph.find(*it + 1);
            while (more != graph.end()) {
                tmplen ++;
                auto tmp = graph.find(*more + 1);
                graph.erase(more);
                more = tmp;
            }
            len = max(len, tmplen);
            graph.erase(it);
        }
        return len;
    }
};
Solution Python


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class Solution:
    # @param num, a list of integer
    # @return an integer
    def longestConsecutive(self, num):
        graph = set()
        for i in num:
            graph.add(i)
        clen = 0
        while graph:
            v = graph.pop()
            tmplen = 1
            less = v - 1
            while less in graph:
                tmplen += 1
                graph.remove(less)
                less -= 1
            more = v + 1
            while more in graph:
                tmplen += 1
                graph.remove(more)
                more += 1
            clen = max(clen, tmplen)
        return clen

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