{ "data": { "question": { "questionId": "3025", "questionFrontendId": "2835", "categoryTitle": "Algorithms", "boundTopicId": 2403635, "title": "Minimum Operations to Form Subsequence With Target Sum", "titleSlug": "minimum-operations-to-form-subsequence-with-target-sum", "content": "
You are given a 0-indexed array nums
consisting of non-negative powers of 2
, and an integer target
.
In one operation, you must apply the following changes to the array:
\n\nnums[i]
such that nums[i] > 1
.nums[i]
from the array.nums[i] / 2
to the end of nums
.Return the minimum number of operations you need to perform so that nums
contains a subsequence whose elements sum to target
. If it is impossible to obtain such a subsequence, return -1
.
A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
\n\n\n
Example 1:
\n\n\nInput: nums = [1,2,8], target = 7\nOutput: 1\nExplanation: In the first operation, we choose element nums[2]. The array becomes equal to nums = [1,2,4,4].\nAt this stage, nums contains the subsequence [1,2,4] which sums up to 7.\nIt can be shown that there is no shorter sequence of operations that results in a subsequnce that sums up to 7.\n\n\n
Example 2:
\n\n\nInput: nums = [1,32,1,2], target = 12\nOutput: 2\nExplanation: In the first operation, we choose element nums[1]. The array becomes equal to nums = [1,1,2,16,16].\nIn the second operation, we choose element nums[3]. The array becomes equal to nums = [1,1,2,16,8,8]\nAt this stage, nums contains the subsequence [1,1,2,8] which sums up to 12.\nIt can be shown that there is no shorter sequence of operations that results in a subsequence that sums up to 12.\n\n
Example 3:
\n\n\nInput: nums = [1,32,1], target = 35\nOutput: -1\nExplanation: It can be shown that no sequence of operations results in a subsequence that sums up to 35.\n\n\n
\n
Constraints:
\n\n1 <= nums.length <= 1000
1 <= nums[i] <= 230
nums
consists only of non-negative powers of two.1 <= target < 231
给你一个下标从 0 开始的数组 nums
,它包含 非负 整数,且全部为 2
的幂,同时给你一个整数 target
。
一次操作中,你必须对数组做以下修改:
\n\nnums[i]
,满足 nums[i] > 1
。nums[i]
从数组中删除。nums
的 末尾 添加 两个 数,值都为 nums[i] / 2
。你的目标是让 nums
的一个 子序列 的元素和等于 target
,请你返回达成这一目标的 最少操作次数 。如果无法得到这样的子序列,请你返回 -1
。
数组中一个 子序列 是通过删除原数组中一些元素,并且不改变剩余元素顺序得到的剩余数组。
\n\n\n\n
示例 1:
\n\n\n输入:nums = [1,2,8], target = 7\n输出:1\n解释:第一次操作中,我们选择元素 nums[2] 。数组变为 nums = [1,2,4,4] 。\n这时候,nums 包含子序列 [1,2,4] ,和为 7 。\n无法通过更少的操作得到和为 7 的子序列。\n\n\n
示例 2:
\n\n\n输入:nums = [1,32,1,2], target = 12\n输出:2\n解释:第一次操作中,我们选择元素 nums[1] 。数组变为 nums = [1,1,2,16,16] 。\n第二次操作中,我们选择元素 nums[3] 。数组变为 nums = [1,1,2,16,8,8] 。\n这时候,nums 包含子序列 [1,1,2,8] ,和为 12 。\n无法通过更少的操作得到和为 12 的子序列。\n\n
示例 3:
\n\n\n输入:nums = [1,32,1], target = 35\n输出:-1\n解释:无法得到和为 35 的子序列。\n\n\n
\n\n
提示:
\n\n1 <= nums.length <= 1000
1 <= nums[i] <= 230
nums
只包含非负整数,且均为 2 的幂。1 <= target < 231
target > sum(nums[i])
, return -1
. Otherwise, an answer existstarget
, independently, from least significant to most significant bit. bit
of target
from least to most significant, let X = sum(nums[i])
for nums[i] <= 2^bit
.X >= 2^bit
, repeatedly select the maximum nums[i]
such that nums[i]<=2^bit
that has not been selected yet, until the sum of selected elements equals 2^bit
. The selected nums[i]
will be part of the subsequence whose elements sum to target, so those elements can not be selected again.\r\nnums[i]
such that nums[i] > 2^bit
, delete nums[i]
and add two occurences of nums[i]/2
. Without moving to the next bit
, go back to the step in hint 3.\\u7248\\u672c\\uff1a \\u7f16\\u8bd1\\u65f6\\uff0c\\u5c06\\u4f1a\\u91c7\\u7528 \\u4e3a\\u4e86\\u4f7f\\u7528\\u65b9\\u4fbf\\uff0c\\u5927\\u90e8\\u5206\\u6807\\u51c6\\u5e93\\u7684\\u5934\\u6587\\u4ef6\\u5df2\\u7ecf\\u88ab\\u81ea\\u52a8\\u5bfc\\u5165\\u3002<\\/p>\"],\"java\":[\"Java\",\" \\u7248\\u672c\\uff1a \\u4e3a\\u4e86\\u65b9\\u4fbf\\u8d77\\u89c1\\uff0c\\u5927\\u90e8\\u5206\\u6807\\u51c6\\u5e93\\u7684\\u5934\\u6587\\u4ef6\\u5df2\\u88ab\\u5bfc\\u5165\\u3002<\\/p>\\r\\n\\r\\n \\u5305\\u542b Pair \\u7c7b: https:\\/\\/docs.oracle.com\\/javase\\/8\\/javafx\\/api\\/javafx\\/util\\/Pair.html <\\/p>\"],\"python\":[\"Python\",\" \\u7248\\u672c\\uff1a \\u4e3a\\u4e86\\u65b9\\u4fbf\\u8d77\\u89c1\\uff0c\\u5927\\u90e8\\u5206\\u5e38\\u7528\\u5e93\\u5df2\\u7ecf\\u88ab\\u81ea\\u52a8 \\u5bfc\\u5165\\uff0c\\u5982\\uff1aarray<\\/a>, bisect<\\/a>, 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