day_30

452. 用最少数量的箭引爆气球

class Solution:     def findMinArrowShots(self, points: List[List[int]]) -> int:         points.sort(key=lambda x:x[0])         r = points[0][1]         cnt = 1         for i in points:             if i[0] > r:                 cnt += 1                 r = i[1]             else:                 r = min(r, i[1])         return cnt 

有趣，之前做过的。

435. 无重叠区间

class Solution:     def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:         if not intervals:             return 0         intervals.sort(key=lambda x: (x[0], x[1]))         res = 1         r = intervals[0][1]         for i in intervals:             if i[0] >= r:                 r = i[1]                 res += 1             else:                 r = min(i[1], r)         return len(intervals) - res 

这题和之前的不就一样的吗，不知道答案在那咔咔写个啥。
763. 划分字母区间

class Solution:     def partitionLabels(self, s: str) -> List[int]:         last = {}         for i, ch in enumerate(s):             last[ch] = i         res = []         start = 0         end = 0         for i, ch in enumerate(s):             end = max(end, last[ch])             if i == end:                 res.append(end - start + 1)                 start = i + 1         return res 

这是很巧妙的想法。