description

You are given a series of video clips from a sporting event that lasted time seconds. These video clips can be overlapping with each other and have varying lengths.

Each video clip is described by an array clips where clips[i] = [starti, endi] indicates that the ith clip started at starti and ended at endi.

We can cut these clips into segments freely.

  • For example, a clip [0, 7] can be cut into segments [0, 1] + [1, 3] + [3, 7].

Return the minimum number of clips needed so that we can cut the clips into segments that cover the entire sporting event [0, time]. If the task is impossible, return -1.

 

Example 1:

Input: clips = [[0,2],[4,6],[8,10],[1,9],[1,5],[5,9]], time = 10
Output: 3
Explanation: We take the clips [0,2], [8,10], [1,9]; a total of 3 clips.
Then, we can reconstruct the sporting event as follows:
We cut [1,9] into segments [1,2] + [2,8] + [8,9].
Now we have segments [0,2] + [2,8] + [8,10] which cover the sporting event [0, 10].

Example 2:

Input: clips = [[0,1],[1,2]], time = 5
Output: -1
Explanation: We cannot cover [0,5] with only [0,1] and [1,2].

Example 3:

Input: clips = [[0,1],[6,8],[0,2],[5,6],[0,4],[0,3],[6,7],[1,3],[4,7],[1,4],[2,5],[2,6],[3,4],[4,5],[5,7],[6,9]], time = 9
Output: 3
Explanation: We can take clips [0,4], [4,7], and [6,9].

 

Constraints:

  • 1 <= clips.length <= 100
  • 0 <= starti <= endi <= 100
  • 1 <= time <= 100

submission

// sort and iterate and simulate steps
// I can't come up with an elegant solution
impl Solution {
    pub fn video_stitching(mut clips: Vec<Vec<i32>>, time: i32) -> i32 {
        // sort by start is enough
        clips.sort();
        let mut ans = 0;
        let mut end = 0;
        let mut idx = 0;
        while idx < clips.len() {
            // we search for the farthest time we
            // can reach each step
            let mut right = end;
            while idx < clips.len() && clips[idx][0] <= end {
                right = right.max(clips[idx][1]);
                idx += 1;
            }
            // if we reach time or we can't go forward, break
            if right <= end || end >= time {
                break;
            }
            // take one clip
            ans += 1;
            end = right;
        }
        // check completeness
        match end >= time {
            true => ans,
            false => -1,
        }
    }
}