1024. Video Stitching

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

Each video clip clips[i] is an interval: it starts at time clips[i][0] and ends at time clips[i][1].  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, T]).  If the task is impossible, return -1.

 

Example 1:

Input: clips = [[0,2],[4,6],[8,10],[1,9],[1,5],[5,9]], T = 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]], T = 5
Output: -1
Explanation: 
We can't 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]], T = 9
Output: 3
Explanation: 
We can take clips [0,4], [4,7], and [6,9].

Example 4:

Input: clips = [[0,4],[2,8]], T = 5
Output: 2
Explanation: 
Notice you can have extra video after the event ends.

 

Constraints:

  • 1 <= clips.length <= 100
  • 0 <= clips[i][0] <= clips[i][1] <= 100
  • 0 <= T <= 100

Rust Solution

struct Solution;

use std::cmp::Reverse;

impl Solution {
    fn video_stitching(mut clips: Vec<Vec<i32>>, t: i32) -> i32 {
        clips.sort_by_key(|v| (v[0], Reverse(v[1])));
        let n = clips.len();
        let mut res = 0;
        let mut left = 0;
        let mut right = 0;
        for i in 0..n {
            if clips[i][0] >= t {
                break;
            }
            if clips[i][0] < left {
                right = right.max(clips[i][1]);
            } else if clips[i][0] <= right {
                right = right.max(clips[i][1]);
                left = right;
                res += 1;
            } else {
                return -1;
            }
        }
        if right < t {
            -1
        } else {
            if left < t {
                res + 1
            } else {
                res
            }
        }
    }
}

#[test]
fn test() {
    let clips = vec_vec_i32![[0, 2], [4, 6], [8, 10], [1, 9], [1, 5], [5, 9]];
    let t = 10;
    let res = 3;
    assert_eq!(Solution::video_stitching(clips, t), res);
    let clips = vec_vec_i32![[0, 1], [1, 2]];
    let t = 5;
    let res = -1;
    assert_eq!(Solution::video_stitching(clips, t), res);
    let clips = vec_vec_i32![
        [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]
    ];
    let t = 9;
    let res = 3;
    assert_eq!(Solution::video_stitching(clips, t), res);
    let clips = vec_vec_i32![[0, 4], [2, 8]];
    let t = 5;
    let res = 2;
    assert_eq!(Solution::video_stitching(clips, t), res);
    let clips = vec_vec_i32![
        [5, 7],
        [1, 8],
        [0, 0],
        [2, 3],
        [4, 5],
        [0, 6],
        [5, 10],
        [7, 10]
    ];
    let t = 5;
    let res = 1;
    assert_eq!(Solution::video_stitching(clips, t), res);
}

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