[Swift]LeetCode1024. 視頻拼接 | Video Stitching

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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 [0,2]. 

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.

Note:

1. 1 <= clips.length <= 100
2. 0 <= clips[i][0], clips[i][1] <= 100
3. 0 <= T <= 100

---

你將會得到一系列視頻片斷，這些片斷來自於一項持續時長爲 T 秒的體育賽事。這些片斷可能有所重疊，也可能長度不一。

視頻片斷 clips[i] 都用區間進行表示：開始於 clips[i][0] 並於 clips[i][1] 結束。咱們甚至能夠對這些片斷自由地再剪輯，例如片斷 [0, 7] 能夠剪切成 [0, 1] + [1, 3] + [3, 7] 三部分。

咱們須要將這些片斷進行再剪輯，並將剪輯後的內容拼接成覆蓋整個運動過程的片斷（[0, T]）。返回所需片斷的最小數目，若是沒法完成該任務，則返回 -1 。

示例 1：

輸入：clips = [[0,2],[4,6],[8,10],[1,9],[1,5],[5,9]], T = 10
輸出：3
解釋：
咱們選中 [0,2], [8,10], [1,9] 這三個片斷。
而後，按下面的方案重製比賽片斷：
將 [1,9] 再剪輯爲 [1,2] + [2,8] + [8,9] 。
如今咱們手上有 [0,2] + [2,8] + [8,10]，而這些涵蓋了整場比賽 [0, 10]。

示例 2：

輸入：clips = [[0,1],[1,2]], T = 5
輸出：-1
解釋：
咱們沒法只用 [0,1] 和 [0,2] 覆蓋 [0,5] 的整個過程。

示例 3：

輸入：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
輸出：3
解釋： 
咱們選取片斷 [0,4], [4,7] 和 [6,9] 。

示例 4：

輸入：clips = [[0,4],[2,8]], T = 5
輸出：2
解釋：
注意，你可能錄製超過比賽結束時間的視頻。

提示：

1. 1 <= clips.length <= 100
2. 0 <= clips[i][0], clips[i][1] <= 100
3. 0 <= T <= 100

---

8ms

 1 class Solution {
 2     func videoStitching(_ clips: [[Int]], _ T: Int) -> Int {
 3         let clips = clips.sorted { first, second in
 4                                   return first[0] < second[0]
 5                                  }
 6         var result = 0
 7         var curEnd = -1
 8         var nextEnd = 0   
 9         for clip in clips {
10             if nextEnd >= T || clip[0] > nextEnd {
11                 break
12             }
13             if curEnd < clip[0] {
14                 result += 1
15                 curEnd = nextEnd
16             }
17             nextEnd = max(clip[1], nextEnd)
18         }
19         return nextEnd >= T ? result : -1
20     }
21 }

---

Runtime: 16 ms

Memory Usage: 18.8 MB

 1 class Solution {
 2     func videoStitching(_ clips: [[Int]], _ T: Int) -> Int {
 3         var last:Int = 0
 4         var cnt:Int = 0
 5         while(true)
 6         {
 7             if last >= T {break}
 8             var found:Bool = false
 9             var mx:Int = -1
10             for i in 0..<clips.count
11             {
12                 if clips[i][0] <= last
13                 {
14                     mx = max(mx, clips[i][1])
15                 }
16             }
17             if mx > last
18             {
19                 last = mx
20                 cnt += 1
21                 found = true
22             }
23             if !found {break}
24         }
25         if last >= T {return cnt}
26         return -1
27     }
28 }