1893

O(n+m) solution

class Solution {
public:
    bool isCovered(vector<vector<int>>& ranges, int left, int right) {
        int line[52] = {};
        for(auto &r : ranges) {
            line[r[0]] += 1;
            line[r[1] + 1] -= 1;
        }
        for(int i = 1, overlaps = 0; i <= right; ++i) {
            overlaps += line[i];
            if (i >= left && overlaps == 0)
                return false;
        }
        return true;
    }
};


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O(nlogn) solution, when range is very large.

public boolean isCovered(int[][] ranges, int left, int right) {
    Arrays.sort(ranges, (x,y)->x[0]-y[0]);
    for(int[] range: ranges)
        if(left >= range[0] && left <= range[1])
            left = range[1] + 1;
    return left > right;
}