lc_352.cpp

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
class SummaryRanges {
public:
    struct Comp {
        bool operator() (const Interval& l, const Interval& r) const {
            return l.start < r.start;
        }
    };
    set< Interval, Comp > ds;
    set< Interval, Comp >::iterator highBound(int val) {
        return ds.upper_bound( Interval(val, val) );
    }
    
    set< Interval, Comp >::iterator lowBound(int val) {
        auto it = ds.lower_bound( Interval(val, val) );
        if (it == ds.begin())
            return ds.end();
        return --it;
    }
    
    /** Initialize your data structure here. */
    SummaryRanges() {
    }
    
    void addNum(int val) {
        auto left = lowBound(val);
        auto right = highBound(val);
        Interval newInterval(val, val);
        if (left != ds.end() && right != ds.end() && left->end + 1 == val && right->start == val + 1) {
            newInterval.start = left->start;
            newInterval.end = right->end;
            ds.erase(left);
            ds.erase(right);
        } else if (left != ds.end() && left->end + 1 >= val) {
            newInterval.start = left->start;
            newInterval.end = max(left->end, val);
            ds.erase(left);
        } else if (right != ds.end() && right->start - 1 == val) {
            newInterval.start = val;
            newInterval.end = right->end;
            ds.erase(right);
        }
        ds.insert( newInterval );
    }
    
    vector<Interval> getIntervals() {
        vector<Interval> res;
        res.reserve(ds.size());
        for (auto e : ds) {
            res.push_back(e);
        }
        return res;
    }
};

/**
 * Your SummaryRanges object will be instantiated and called as such:
 * SummaryRanges obj = new SummaryRanges();
 * obj.addNum(val);
 * vector<Interval> param_2 = obj.getIntervals();
 */