题目
17. Letter Combinations of a Phone Number
Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telephone buttons) is given below.
用户按数字键，程序输出所有的可能组合。
What's Next?
题目
What’s Next?
Johnny is playing with a large binary number, B. The number is so large that it needs to be compressed into an array
of integers, A, where the values in even indices (0, 2, 4,...) represent some number of consecutive 1 bits and
the values in odd indices (1, 3, 5,...) represent some number of consecutive 0 bits in alternating substrings of B.
For example, suppose we have array A = {4, 1, 3, 2, 4}. A0 represents "1111", A1
represents "0", A2 represents "111", A3 represents "00", and A4 represents
"1111". The number of consecutive binary characters in ith the substring of B corresponds to integer
Ai, as shown in this diagram:
When we assemble the sequential alternating sequences of 1‘s and 0‘s, we get B = 11110111001111.
We define setCount(B) to be the number of 1‘s in a binary number, B. Johnny wants to find a binary number, D,
that is the smallest binary number > B where setCount(B) = setCount(D). He then wants to compress D into an
array of integers, C (in the same way that integer array A contains the compressed form of binary string B).
Johnny isn’t sure how to solve the problem. Given array A, find integer array C and print its length on a new line. Then print the elements of array C as a single line of space-separated integers.