※ 引述《RockLee (Now of all times)》之铭言：
: 原始网址:
: http://www.careercup.com/question?id=14539805
: 题目:
: Three strings say A, B, C are given to you.
: Check weather 3rd string is interleaved from string A and B.
: Ex: A="abcd" B="xyz" C="axybczd". answer is yes. o(n)
: 用 Dynamic Programming 应该可在 O(n^2) 的时间内解决
: 但要在 O(n) 的时间内解决就想不出来了 Orz...
: CareerCup 上的讨论看来都无法在 O(n) 的时间内正确的解决
: 不知道板上有没有人有什么 idea?
这是一个很快的想法, 我不知道对不对,
反正大家讨论一下.
You can put two flags on string A and B,
then scan every character in C.
for example, the first step,
it will be, A = a | bcd and B = | xyz.
then it's not hard to see if the flag of A,B move to the end.
One problem is the one it points out in the webpage.
if A = 'ca', B = 'cb' , C = 'cacb' or 'cbca' should be both true.
So, when you scan the character, you need to put an additional index
to handle the duplicate character.
In this situation, C = 'cacb', when you do the scan of the fist char
A = c | a and B = c | b, but both has index = 1.
In the next step, you scan second char, which is a,
Now, A = 'c a |' and you reset the index of A into 0.
at the same time you push the flag of B back with 1.
So B = '| c b'.
This should be running in a linear time?