LeetCode刷题_56_合并区间

思路：也没啥好说的了，就是模拟然后注意输入可能为空的判断。运用运算符重载先sort一波。应该有更简单的解法，待我研究出来再更新。

class Solution {
public:
    static bool cmp(pair<int, int> P1, pair<int, int> P2) {
        if(P1.first != P2.first) {
            return P1.first < P2.first;
        }
        return P1.second < P2.second;
    }
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
        if(intervals.size() == 0) {
            return intervals;
        }
        vector<pair<int, int>> v;
        for(int i = 0; i < intervals.size(); ++i) {
            v.push_back(pair<int, int>(intervals[i][0], intervals[i][1]));
        }    
        sort(v.begin(), v.end(), cmp);
        pair<int, int> temp = v[0];
        vector<pair<int, int>> ans;
        for(int i = 1; i < v.size(); ++i) {
            if(temp.second >= v[i].first) {
                if(temp.second <= v[i].second)
                    temp = pair<int, int>(temp.first, v[i].second);
            }
            else {
                ans.push_back(temp);
                temp = v[i];
            }
        }
        ans.push_back(temp);
        vector<vector<int>> f;
        for(int i = 0; i < ans.size(); ++i) {
            vector<int>sb;
            sb.push_back(ans[i].first); sb.push_back(ans[i].second);
            f.push_back(sb);
        }
        return f;
    }
private:
};