1. Two Sum
Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution.
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
UPDATE (2016/2/13):
The return format had been changed to zero-based indices. Please read the above updated description carefully.
注：给出一个整数向量，和一个目标值，找出向量中加和等于目标值的那两个数所在的位置。（假如只有一组解） （位置索引是从0开始）
6. ZigZag Conversion
The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
P A H N
A P L S I I G
Y I R
And then read line by line: "PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a number of rows:
string convert(string text, int nRows);
convert("PAYPALISHIRING", 3) should return "PAHNAPLSIIGYIR".
注：把一串字母按照"z"形排列，现在要按行读出来。（不懂）
查了一下是这个样子：text="PAYPALISHIRING" , nRows=4 时
P I N
A L S I G
Y A H R
P I
结果是 "PINALSIGYAHRPI".
要弄清楚规律，按列存储一个字符串，然后按行读出来