代码随想录刷题第三十六天| 435. 无重叠区间 ● 763.划分字母区间 ● 56. 合并区间

代码随想录刷题第三十六天

无重叠区间 (LC 435)

题目思路：

代码实现：

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

划分字母区间 (LC 763)

题目思路：

这道题思路有点难想，如果能够想到使用position数组记录每个字母最后出现的位置后，题目及代码就比较好解了

代码实现：

class Solution:
    def partitionLabels(self, s: str) -> List[int]:
        res = []
        pos = [0 for _ in range(len(s))]
        storage = {
   }
        for i in range(len(s)-1, -1, -1):
            if s[i] not in storage.keys():
                pos[i] = i
                storage[s[i]] = i
            else:
                pos[i] = storage[s[i]]
        
        last = pos[0]
        start = 0
        for i in range(len(pos)):
            last = max(last, pos[i])
            if last == i:
                res.append(i-start+1)
                start = i+1

        return res

合并区间 (LC 56)

题目思路：

代码实现：

class Solution:
    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
        intervals.sort(key=lambda x:x[0])

        left = intervals[0][0]
        right = intervals[0][1]
        result = []
        for i in range(1, len(intervals)):
            if intervals[i][0]<=right:
                right = max(right, intervals[i][1])
            else:
                result.append([left, right])
                left = intervals[i][0]
                right = intervals[i][1]
        result.append([left, right])

        return result