163. Missing Ranges (Medium)

Given a sorted integer array where the range of elements are in the inclusive range [lower, upper], return its missing ranges.

For example, given [0, 1, 3, 50, 75], lower = 0 and upper = 99, return ["2", "4->49", "51->74", "76->99"].

Solution:

要考虑overflow, 这里要用long

vector<string> findMissingRanges(vector<int>& nums, int lower, int upper) {
    long l = lower; // first missing integer
    vector<string> res;
    for (int i = 0; i <= nums.size(); ++i) {
        // current occurred integer
        long r = (i == nums.size() || nums[i] > upper) ? (long)upper+1:nums[i];
        if (l == r) ++l; // not missing
        else if (l < r) {
            res.push_back((r == l+1) ? to_string(l):to_string(l)+"->"+to_string(r-1));
            l = r+1;
        }
        if (r >= upper) break;
    }
    return res;
}