标签：
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.
分析：主要用map来记录nums[i]是否检查过。检查过则从map中删除，同时检查nums[i] + 1和nums[i] - 1。
运行时间：40ms
1 class Solution { 2 public: 3 int longestConsecutive(vector<int>& nums) { 4 map<int, int> hashmap; 5 for(int i = 0; i < nums.size(); i++) hashmap.insert(map<int, int>::value_type(nums[i], i)); 6 7 int longest = 1; 8 map<int, int>::iterator ite; 9 for(ite = hashmap.begin(); ite != hashmap.end(); ite++){ 10 int len = 1; 11 12 int j = ite->first + 1; 13 for(; hashmap.find(j) != hashmap.end(); j++){ 14 len++; 15 hashmap.erase(j); 16 } 17 int k = ite->first - 1; 18 for(; hashmap.find(k) != hashmap.end(); k--){ 19 len++; 20 hashmap.erase(k); 21 } 22 longest = max(longest, len); 23 } 24 return longest; 25 } 26 };
标签：
原文地址：http://www.cnblogs.com/amazingzoe/p/4493854.html
