LeetCode --- Longest Consecutive Sequence

对unordered_set和set的内部实现还不了解，只知道前者是hash实现的，后者是用R-B-Tree实现。有时间需要读下源码。

附上代码：

 1 class Solution {
 2 public:
 3     int longestConsecutive(vector<int> &num) {
 4         unordered_set<int> mynum(num.begin(), num.end());
 5         // "max_len" holds the length of the longest consecutive sequence
 6         int max_len(0);
 7         // "N" is the length of "num"
 8         unsigned int N(num.size());
 9         // iterator every element of vector num
10         for (unsigned int i(0); i < N; i++) {
11             // "count" holds the maximum length of 
12             //  consecutive sequence that can be found 
13             //  by expanding from "num[i]" to the left and right
14             int count(0), tmp(num[i]);
15             while (mynum.find(tmp) != mynum.end()) {
16                 // erase "tmp" from set
17                 mynum.erase(tmp);
18                 count++;
19                 // since "INT_MAX + 1 = INT_MIN"
20                 // we should not consider {INT_MAX-1, INT_MAX, INT_MIN} as consecutive sequence 
21                 if (tmp == INT_MAX) break;
22                 tmp++;
23             }
24             tmp = nu