Uber OA has just ended, so I’ll write and share while it’s hot to build up my character. My game has a three-question structure, and the overall difficulty level is roughly as follows: People with a solid foundation will find it smooth, while people who usually only answer scattered questions may find it a bit stuck. Let’s talk about the idea below.
Question 1: Minimum number of power operations
Given a positive integer N, each operation can add or subtract an integer power of 2 (2^i,I≥0).
Requirements: The calculation will N Become 0 Minimum number of operations required.
Problem-solving ideas
The goal of the addition and subtraction operations is to maximize the elimination of 1 in the binary representation. When the last two digits are 11, perform a +1 operation to eliminate consecutive 1s. When the last two digits are 01, perform a -1 operation to eliminate a single 1. When the last two digits are 0, directly shift one to the right. Continuously check the last two digits of the binary representation of the value: 11 → perform +1, 01 → perform -1, 0X → shift one to the right. Until the value reaches zero, count the total number of operations.
Topic 2: Calculation of final product pricing
Given an array of product prices, the final price of each product = original price – the first one on the right ≤ its price (if not, the original price will be used).
Requirements: Output the sum of the final price of all items, and the 0-based index (space separated in ascending order) of the items sold at their original price.
Problem-solving ideas
For each p[i], if there is one less than or equal to it on its right, then find the first p[j] that is less than or equal to it, and the value of p[i] will become p[i] – p[j], otherwise it will remain unchanged. Let us output all the final values and the item subscripts that have not changed, and just use a monotonic stack to maintain it.
Question 3: Balanced Number Determination
Given a permutation array p of 1~n, if there is an interval [l,r] such that the numbers in the interval are exactly permutations of 1~k, then k is a balanced number.
Requirement: Determine whether each k from 1 to n is balanced, and return a binary string of length n (the k-th bit is 1 to indicate balance, and 0 to indicate balance).
Problem-solving ideas
Consider asking us to find 1~n. For each i, does [1,i] all appear in an interval, and there are no other numbers. Obviously [1,i] can be pushed to [1,i + 1], and is only related to the left and right endpoints [l,r] of [1,i]. We maintain a leftmost and rightmost. If r – l + 1 is exactly equal to i, then it is legal, otherwise it is illegal.
Learn more
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