solve.cpp

#include <unordered_map>
#include <vector>
#include <string>
#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <algorithm>
using namespace std;
class Solution {
	public:
		int longestConsecutive(vector<int> &nums) {
			unordered_map<int, int> map;
			int res = 0;
			for (int i : nums) {
				if (map.find(i) != map.end()) {
					continue;
				}
				int left = getOrElse(map, i - 1);
				int right = getOrElse(map, i + 1);
				int sum = left + right + 1;
				res = max(res, sum);
				map[i] = sum;
				map[i - left] = sum;
				map[i + right] = sum;
			}
			return res;
		}
	private:
		int getOrElse(unordered_map<int, int> &map, int key, int defaultValue) {
			if (map.find(key) != map.end()) {
				return map[key];
			} else
				return defaultValue;
		}
		int getOrElse(unordered_map<int, int> &map, int key) {
			return getOrElse(map, key, 0);
		}
};
int main(int argc, char **argv)
{
	Solution solution;
	int n;
	while (scanf("%d", &n) != EOF) {
		vector<int> nums;
		for (int i = 0; i < n; ++i) {
			int v;
			scanf("%d", &v);
			nums.push_back(v);
		}
		printf("%d\n", solution.longestConsecutive(nums));
		break;
	}
	return 0;
}