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.
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public
class
Solution { public
int
longestConsecutive(int[] num) { int
length = 0; if(num.length > 0){ length = 1; Map<Integer, Integer> lens = new
HashMap<Integer, Integer>(); Map<Integer, Integer> visited = new
HashMap<Integer, Integer>(); for(int
i = 0; i < num.length; ++i){ lens.put(num[i], 1); visited.put(num[i], 0); } for(int
i = 0; i < num.length; ++i){ if(visited.get(num[i]) != 0) continue; else{ visited.put(num[i], 1); if(lens.containsKey(num[i] - 1)){ if(visited.get(num[i] - 1) == 0){ int
templength = lens.get(num[i] - 1) + lens.get(num[i]); lens.put(num[i], templength); lens.put(num[i] - lens.get(num[i] - 1), templength); length = (length < templength)? templength: length; visited.put(num[i] - 1, 1); } } if(lens.containsKey(num[i] + 1)){ int
templength = lens.get(num[i] + 1) + lens.get(num[i]); lens.put(num[i] - lens.get(num[i]) + 1, templength); lens.put(num[i] + lens.get(num[i] + 1), templength); length = (length < templength)? templength: length; } } } } return
length; }} |
leetcode--Longest Consecutive Sequence
原文：http://www.cnblogs.com/averillzheng/p/3535481.html