defright_bisect(hay, needle):# upper-bound lo, hi = 0, len(hay) while lo < hi: # 左闭右开区间,只有严格小于时才表示搜索区间为空 mid = lo + (hi - lo) // 2 if hay[mid] > needle: # g(x)的意义就是找到大于needle的最小index hi = mid # g(x)为True,那说明在成立的一侧,最小值在左边 else: lo = mid + 1 return lo # 始终没有找到使g(x)=True,返回hi
defleft_bisect(hay, needle):# lower-bound lo, hi = 0, len(hay) while lo < hi: mid = lo + (hi - lo) // 2 if hay[mid] >= needle: # g(x)的意义就是找到大于等于needle的最小index hi = mid else: lo = mid + 1 return lo
defkth(self, matrix, k): lo, hi = matrix[0][0], matrix[-1][-1]+1 while lo < hi: mid = (lo + hi) // 2 small_cnt = 0 for row in matrix: small_cnt += bisect_right(row, mid) if small_cnt >= k: hi = mid else: lo = mid + 1 return lo
A conveyor belt has packages that must be shipped from one port to another within D days.
The i-th package on the conveyor belt has a weight of weights[i]. Each day, we load the ship with packages on the conveyor belt (in the order given by weights). We may not load more weight than the maximum weight capacity of the ship.
Return the least weight capacity of the ship that will result in all the packages on the conveyor belt being shipped within D days.
Example 1: Input: weights = [1,2,3,4,5,6,7,8,9,10], D = 5 Output: 15 Explanation: A ship capacity of 15 is the minimum to ship all the packages in 5 days like this: 1st day: 1, 2, 3, 4, 5 2nd day: 6, 7 3rd day: 8 4th day: 9 5th day: 10
Note that the cargo must be shipped in the order given, so using a ship of capacity 14 and splitting the packages into parts like (2, 3, 4, 5), (1, 6, 7), (8), (9), (10) is not allowed.
defmin_cap(weights, D): defdays_needed(cap): k = 1 this_ship_weight = 0 for x in weights: this_ship_weight += x if this_ship_weight > cap: this_ship_weight = x k += 1 return k lo, hi = max(weights), sum(weights) while lo <= hi: mid = (lo + hi) // 2 if days_needed(mid) <= D: hi = mid - 1 else: lo = mid + 1 return lo