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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 <= clips.length <= 100
0 <= clips[i][0], clips[i][1] <= 100
0 <= T <= 100
思路:
DP,dp[i]表示从0到i位置都有的情况下,选取的最小值
然后每来一个新的Interval【s,t】,更新dp[s]..dp[t],复杂度正好10^6
为了保证interval.s小的先算,先排下序就完了
class Solution(object):
def videoStitching(self, clips, T):
"""
:type clips: List[List[int]]
:type T: int
:rtype: int
"""
clips.sort(key=lambda a:a[0])
dp=[float('inf')]*(T+1)
dp[0] = 0
for s,t in clips:
for i in range(s,min(t,T)+1):
for j in range(s,i):
dp[i]=min(dp[i], dp[j]+1)
return dp[T] if dp[T]<float('inf') else -1