题目描述

Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (not unary) +, -, or * between the digits so they evaluate to the target value.

Example 1:

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Input: num = "123", target = 6
Output: ["1+2+3", "1*2*3"]

Example 2:

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Input: num = "232", target = 8
Output: ["2*3+2", "2+3*2"]

Example 3:

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Input: num = "105", target = 5
Output: ["1*0+5","10-5"]

Example 4:

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Input: num = "00", target = 0
Output: ["0+0", "0-0", "0*0"]

Example 5:

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Input: num = "3456237490", target = 9191
Output: []

题目描述

Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...) which sum to n.

Example 1:

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Input: n = 12
Output: 3 
Explanation: 12 = 4 + 4 + 4.

Example 2:

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Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.

题目描述

You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.

Suppose you have n versions [1, 2, ..., n] and you want to find out the first bad one, which causes all the following ones to be bad.

You are given an API bool isBadVersion(version) which will return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.

Example:

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Given n = 5, and version = 4 is the first bad version.

call isBadVersion(3) -> false
call isBadVersion(5) -> true
call isBadVersion(4) -> true

Then 4 is the first bad version.

题目描述

Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a function to compute the researcher’s h-index.

According to the definition of h-index on Wikipedia: “A scientist has index h if h of his/her N papers have at least h citations each, and the other N − h papers have no more than h citations each.”

Example:

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Input: citations = [0,1,3,5,6]
Output: 3 
Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had 
             received 0, 1, 3, 5, 6 citations respectively. 
             Since the researcher has 3 papers with at least 3 citations each and the remaining 
             two with no more than 3 citations each, her h-index is 3.

题目描述

Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher’s h-index.

According to the definition of h-index on Wikipedia: “A scientist has index h if h of his/her N papers have at least hcitations each, and the other N − h papers have no more than h citations each.”

Example:

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Input: citations = [3,0,6,1,5]
Output: 3 
Explanation: [3,0,6,1,5] means the researcher has 5 papers in total and each of them had 
             received 3, 0, 6, 1, 5 citations respectively. 
             Since the researcher has 3 papers with at least 3 citations each and the remaining 
             two with no more than 3 citations each, her h-index is 3.

题目描述

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.

Example 1:

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Input: [3,0,1]
Output: 2

Example 2:

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Input: [9,6,4,2,3,5,7,0,1]
Output: 8

题目描述

Write a program to find the n-th ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.

Example:

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Input: n = 10
Output: 12
Explanation: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers.

题目描述

Write a program to check whether a given number is an ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.

Example 1:

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Input: 6
Output: true
Explanation: 6 = 2 × 3

Example 2:

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Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2

Example 3:

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Input: 14
Output: false 
Explanation: 14 is not ugly since it includes another prime factor 7.

题目描述

Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.

Example:

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Input:  [1,2,1,3,2,5]
Output: [3,5]

题目描述

Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.

Example:

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Input: 38
Output: 2 
Explanation: The process is like: 3 + 8 = 11, 1 + 1 = 2. 
             Since 2 has only one digit, return it.