Given an integer array nums, return the number of range sums that lie in [lower, upper] inclusive. Range sum S(i, j) is defined as the sum of the elements in nums between indices i and j (i ≤ j), inclusive.

Note:

A naive algorithm of O(n2) is trivial. You MUST do better than that.

Example:

Given nums = [-2, 5, -1], lower = -2, upper = 2,

Return 3.

The three ranges are : [0, 0], [2, 2], [0, 2] and their respective sums are: -2, -1, 2.

Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10n.

Example:

Given n = 2, return 91. (The answer should be the total numbers in the range of 0 ≤ x < 100, excluding [11,22,33,44,55,66,77,88,99])

Hint:

• A direct way is to use the backtracking approach.
• Backtracking should contains three states which are (the current number, number of steps to get that number and a bitmask which represent which number is marked as visited so far in the current number). Start with state (0,0,0) and count all valid number till we reach number of steps equals to 10n.
• This problem can also be solved using a dynamic programming approach and some knowledge of combinatorics.
• Let f(k) = count of numbers with unique digits with length equals k.
• f(1) = 10, …, f(k) = 9 * 9 * 8 * … (9 - k + 2) [The first factor is 9 because a number cannot start with 0].

Given two strings s and t, write a function to determine if t is an anagram of s.

For example,

s = “anagram”, t = “nagaram”, return true. s = “rat”, t = “car”, return false.

Note:

You may assume the string contains only lowercase alphabets.

Follow up:

What if the inputs contain unicode characters? How would you adapt your solution to such case?

Given a collection of intervals, merge all overlapping intervals.

For example,

Given [1,3],[2,6],[8,10],[15,18],

return [1,6],[8,10],[15,18].

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Your goal is to reach the last index in the minimum number of jumps.

For example:

Given array A = [2,3,1,1,4]

The minimum number of jumps to reach the last index is 2. (Jump 1 step from index 0 to 1, then 3 steps to the last index.)

Note:

You can assume that you can always reach the last index.

Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1.

Examples:

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s = "leetcode"
return 0.

s = "loveleetcode",
return 2.

Note:

You may assume the string contain only lowercase letters.

Given a binary tree, return the postorder traversal of its nodes’ values.

For example:

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Given binary tree {1,#,2,3},
   1
    \
     2
    /
   3

return [3,2,1].

Note:

Recursive solution is trivial, could you do it iteratively?

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times) with the following restrictions:

You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again). After you sell your stock, you cannot buy stock on next day. (ie, cooldown 1 day)

Example:

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prices = [1, 2, 3, 0, 2]
maxProfit = 3
transactions = [buy, sell, cooldown, buy, sell]

Validate if a given string is numeric.

Some examples:

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"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true

Note:

It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.