Minimum Time Difference

0539.Minimum-Time-Difference/memo.md

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+# 539. Minimum Time Difference
+
+## step1
+ソートする解法はすぐに思いつく。10m。日をまたぐ差分を考慮せずに一度間違えた。
+計算量O(nlogn)
+
+## step2
+変数名を改善。
+
+https://leetcode.com/problems/minimum-time-difference/editorial/?envType=problem-list-v2&envId=7p55wqm
+
+バケットソート。全く思いつかなかった。ソート対象の値が限られているときにバケットソートが使えることを覚えておきたい。
+計算量 O(1)
+
+## step3
+
+sortedcontainers.SortedList: 検索、追加、削除が 平均O(logN)で可能なデータ構造（最悪はO(N)）
+
+一定サイズに分割した二重配列_lists、部分配列の最大値を格納した_maxes、要素数を木構造で管理する_index で管理している
+
+https://grantjenks.com/docs/sortedcontainers/introduction.html
+
+https://github.com/grantjenks/python-sortedcontainers/tree/master/src/sortedcontainers

0539.Minimum-Time-Difference/step1_sort.py

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+class Solution:
+    def findMinDifference(self, timePoints: List[str]) -> int:
+        def time_to_minutes(time_point: str):
+            hours, minutes = time_point.split(":")
+            return 60 * int(hours) + int(minutes)
+
+        minutes = [time_to_minutes(time_point) for time_point in timePoints]
+        minutes.sort()
+        minutes.append(minutes[0] + 24 * 60)
+
+        min_difference = float("inf")
+        for i in range(len(minutes) - 1):
+            min_difference = min(min_difference, minutes[i+1] - minutes[i])
+
+        return min_difference
+
+

0539.Minimum-Time-Difference/step2_backet_sort.py

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+class Solution:
+    def findMinDifference(self, timePoints: List[str]) -> int:
+        MINUTES_IN_DAY = 24 * 60
+
+        if len(timePoints) > MINUTES_IN_DAY:
+            return 0
+
+        def time_to_minutes(time_point: str) -> int:
+            hours, minutes = time_point.split(":")
+            return int(hours) * 60 + int(minutes)
+
+        seen = [False] * MINUTES_IN_DAY
+        for time_point in timePoints:
+            time_in_minutes = time_to_minutes(time_point)
+            if seen[time_in_minutes]:
+                return 0
+            seen[time_in_minutes] = True
+
+        min_difference = float("inf")
+        previous_time = None
+        first_time = None
+        last_time = None
+        for time_in_minutes in range(len(seen)):
+            if not seen[time_in_minutes]:
+                continue
+
+            if first_time is None:
+                first_time = time_in_minutes
+                previous_time = time_in_minutes
+                continue
+
+            min_difference = min(min_difference, time_in_minutes - previous_time)
+            previous_time = time_in_minutes
+            last_time = time_in_minutes
+
+        min_difference = min(min_difference, first_time - last_time + MINUTES_IN_DAY)
+
+        return min_difference

0539.Minimum-Time-Difference/step2_sort.py

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+class Solution:
+    def findMinDifference(self, timePoints: List[str]) -> int:
+        MINUTES_IN_DAY = 24 * 60
+
+        def time_to_minutes(time_point: str) -> int:
+            hours, minutes = time_point.split(":")
+            return int(hours) * 60 + int(minutes)
+
+        times_in_minutes = sorted(time_to_minutes(time_point) for time_point in timePoints)
+        times_in_minutes.append(times_in_minutes[0] + MINUTES_IN_DAY)
+
+        min_difference = float("inf")
+        for i in range(len(times_in_minutes) - 1):
+            min_difference = min(min_difference, times_in_minutes[i+1] - times_in_minutes[i])
+
+        return min_difference

0539.Minimum-Time-Difference/step3_SortedList.py

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+from sortedcontainers import SortedList
+
+class Solution:
+    def findMinDifference(self, timePoints: list[str]) -> int:
+        MINUTES_IN_DAY = 24 * 60
+
+        if len(timePoints) > MINUTES_IN_DAY:
+            return 0
+
+        def time_to_minutes(time_point: str) -> int:
+            h, m = time_point.split(":")
+            return int(h) * 60 + int(m)
+
+        sorted_time_points = SortedList()
+        min_difference = float("inf")
+
+        for tp in timePoints:
+            time_in_minutes = time_to_minutes(tp)
+            if time_in_minutes in sorted_time_points:
+                return 0
+
+            index = sorted_time_points.bisect_left(time_in_minutes)
+
+            if index < len(sorted_time_points):
+                min_difference = min(min_difference, sorted_time_points[index] - time_in_minutes)
+            elif sorted_time_points:
+                min_difference = min(min_difference, sorted_time_points[0] + 1440 - time_in_minutes)
+
+            if index > 0:
+                min_difference = min(min_difference, time_in_minutes - sorted_time_points[index - 1])
+            elif sorted_time_points:
+                min_difference = min(min_difference, time_in_minutes + 1440 - sorted_time_points[-1])
+
+            sorted_time_points.add(time_in_minutes)
+
+        return min_difference

0539.Minimum-Time-Difference/step3_backet_sort.py

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+class Solution:
+    def findMinDifference(self, timePoints: List[str]) -> int:
+        MINUTES_IN_DAY = 24 * 60
+
+        if len(timePoints) > MINUTES_IN_DAY:
+            return 0
+
+        def time_to_minutes(time_point: str) -> int:
+            h, m = time_point.split(":")
+            return int(h) * 60 + int(m)
+
+        seen = [False] * MINUTES_IN_DAY
+        for time_point in timePoints:
+            time_in_minutes = time_to_minutes(time_point)
+            if seen[time_in_minutes]:
+                return 0
+            seen[time_in_minutes] = True
+
+        min_difference = float("inf")
+        previous_time = None
+        first_time = None
+        for time_in_minutes in range(len(seen)):
+            if not seen[time_in_minutes]:
+                continue
+
+            if first_time is None:
+                first_time = time_in_minutes
+                previous_time = time_in_minutes
+                continue
+
+            min_difference = min(min_difference, time_in_minutes - previous_time)
+            previous_time = time_in_minutes
+
+        min_difference = min(min_difference, first_time - previous_time + MINUTES_IN_DAY)
+
+        return min_difference