递归二分

1014. Capacity To Ship Packages Within D Days.py

@@ -0,0 +1,40 @@
+class Solution:
+    def shipWithinDays(self, weights: List[int], D: int) -> int:
+        """
+        解法：二分搜索
+        target = D，也就是说，当天数恰好为D时，返回重量。
+        """
+
+        def count_days(weight):
+            """
+            当重量为weight时，返回需要的天数
+            """
+            if weight < mi:
+                return D + 1
+            count = 1
+            tem = weight
+            for x in weights:
+                if tem >= x:
+                    tem -= x
+                else:
+                    count += 1
+                    tem = weight - x
+            return count
+
+        def bin_search(low, high):
+            if low > high:
+                return low
+            mid = (low + high) // 2
+            days = count_days(mid)
+            print(mid, days)
+            if days <= D:
+                return bin_search(low, mid - 1)
+            else:
+                return bin_search(mid + 1, high)
+
+        if len(weights) < D:
+            return max(weights)
+        mi = max(weights)
+        ma = sum(weights)
+        return bin_search(mi, ma)
+