Leetcode刷题笔记1 贪心算法part04

leetcode 452 用最小数量的箭引爆气球

本题被如何更新边界考住了

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

leetcode 435 无重叠区间

卡在更新右边界了

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

leetcode 763 划分字母区间

在寻找切割点时，关于区间的更新使用end = max(end, distance[value]) 如果i==end那么说明在区间[start, end]中已经包含了所有的元素，区间外没有重复元素。

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