2024-01-03 无重叠区间

435. 无重叠区间

思路：和最少数量引爆气球的箭的思路基本都是一致了！贪心就是比较左边的值是否大于下一个右边的值

class Solution:
    def eraseOverlapIntervals(self, points: List[List[int]]) -> int:
        points.sort(key=lambda x: (x[0], x[1]))
        # 比较边界
        res = points[0][1]
        count = 0
        for i in range(1, len(points)):
            if points[i][0] < res:
                res = min(res, points[i][1])
                count += 1
            else:
                res = points[i][1]
        return count

763. 划分字母区间

贪心思路：第一个字母最后出现的位置的过程中其他字母也出现的最后位置的最大值，就是一次划分区域了！

class Solution:
    def partitionLabels(self, s: str) -> List[int]:
        # 字母出现次数？
        # 每一次字母最后出现的位置以及
        mm = {
   }
        for i in range(len(s)):
            mm[s[i]] = i
        start = 0
        max_temp = mm[s[0]]
        res = []
        for i in range(len(s)):
            if max_temp == i:
                res.append(max_temp - start + 1)
                start = i + 1
                if i + 1 < len(s):
                    max_temp = mm[s[i + 1]]
            elif mm[s[i]] > max_temp:
                max_temp = mm[s[i]]
        return res
    
class Solution:
    def partitionLabels(self, s: str) -> List[int]:
        last_occurrence = {
   }  # 存储每个字符最后出现的位置
        for i, ch in enumerate(s):
            last_occurrence[ch] = i

        result = []
        start = 0
        end = 0
        for i, ch in enumerate(s):
            end = max(end, last_occurrence[ch])  # 找到当前字符出现的最远位置
            if i == end:  # 如果当前位置是最远位置，表示可以分割出一个区间
                result.append(end - start + 1)
                start = i + 1

        return result

56. 合并区间

思路：就是如果区间的重叠的哇，就去重叠区间之间的最小值和最大值!关键还是拆分排序

class Solution:
    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
        res = []
        intervals.sort(key=lambda x :(x[0], x[1]))
        index = 0
        max_broad = intervals[0][1]
        for i in range(1, len(intervals)):
            if intervals[i][0] <= max_broad:
                intervals[index][0] = min(intervals[index][0], intervals[i][0])
                intervals[index][1] = max(intervals[index][1], intervals[i][1])
                max_broad = intervals[index][1]
            else:
                res.append(intervals[index])
                index = i
                max_broad = intervals[i][1]
        if intervals[index] not in res:
            res.append(intervals[index])
        return res