Leetcode 贪心 Longest Consecutive Sequence

Longest Consecutive Sequence

Total Accepted: 19169 Total
Submissions: 68303My Submissions

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.

题意：最长连续序列

思路：贪心

复杂度：时间 O(n)，空间O(1)

int longestConsecutive(vector<int> &num){
	if(num.empty()) return 0;
	int _max = 1;
	int count = 1;
	sort(num.begin(), num.end());
	for(int pre = num[0], i = 1; i < num.size(); ++i){
		if(num[i] == pre + count) count++;
		else if(num[i] == num[i - 1]) continue; //要注意相等的情况
		else{
			_max = max(_max, count);
			pre = num[i];
			count = 1;
		}
	}
	return max(_max, count);
}