day30 第八章 贪心算法 part04

452. 用最少数量的箭引爆气球

先排序，再算重叠区间

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

435. 无重叠区间

跟上一题一样

class Solution:def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:# if len(intervals)==0:#     return 0intervals.sort(key = lambda x:x[0])result = 0for i in range(1, len(intervals)):if intervals[i][0] < intervals[i-1][1]:continueelse:result += 1intervals[i][1] = min(intervals[i][1], intervals[i-1][1])return result

763.划分字母区间

先准备一下每个字母的最大位置，以便后续继续计算。

class Solution:def partitionLabels(self, s: str) -> List[int]:# 求得字母的最远位置alphebet_dict = dict()for i in range(len(s)):alphebet_dict[s[i]] = i# 遍历，求得每一个片段内能容纳多少字母end = 0start = 0result = []for i in range(len(s)):end = max(end, alphebet_dict[s[i]])if end == i:result.append(end-start+1)start = i+1return result