57. Insert Interval

O(n) time O(1) space

class Solution {
public:
    vector<vector<int>> insert(vector<vector<int>>& intervals, vector<int>& newInterval) {
        vector<vector<int>> res;
        int i = 0, n = intervals.size();
        for (; i < n && intervals[i][0] < newInterval[0]; ++i) {
            res.push_back(intervals[i]);
        }
        if (!res.empty() && newInterval[0] <= res.back()[1]) {
            res.back()[1] = max(res.back()[1], newInterval[1]);
        } else {
            res.push_back(newInterval);
        }
        for (; i < n; ++i) {
            if (intervals[i][0] <= res.back()[1]) {
                res.back()[1] = max(res.back()[1], intervals[i][1]);
            } else {
                res.push_back(intervals[i]);
            }
        }
        return res;
    }
};

/**
 * 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 Solution {
public:
    vector<Interval> insert(vector<Interval>& intervals, Interval newInterval) {
        vector<Interval> res;
        int i = 0;
        int n = intervals.size();
        for (; i < n && intervals[i].start < newInterval.start; ++i) {
            res.push_back(intervals[i]);
        }
        if (!res.empty() && newInterval.start <= res.back().end) {
            res.back().end = max(res.back().end, newInterval.end);
        } else {
            res.push_back(newInterval);
        }
        for (int j = i; j < n; ++j) {
            if (intervals[j].start <= res.back().end) {
                res.back().end = max(res.back().end, intervals[j].end);
            } else {
                res.push_back(intervals[j]);
            }
        }
        return res;
    }
};