GFG 67 Common String

You are given two strings s and t. You have to  nd a string with the minimum length that contains

both s and t as substrings. If there are multiple such strings return the lexicographically smallest

one.

Example 1:

Input:

s = "asdfg"

t = "fghj"

Output:

"asdfghj"

Explanation:

The string "asdfghj" contains s and t both as substrings.

Example 2:

Input:

s = "bacbab"

t = "aba"

Output:

"abacbab"

Explanation:

The possible two strings of length 7 are "abacbab"

and "bacbaba". But the string "abacbab" is lexicographically

smaller.

Your Task:  

You don't need to read input or print anything. Your task is to complete the

function commonString() which takes two strings s and t as input parameters and returns the

required string.

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找最短的长度，如果长度一样，就找最小的字典序的字符串，

因为不知道哪种情况最短，就两个办法都放进去，

Join(a,b), Join(b,a)

然后写个方法join,就是b的前缀跟a的后缀去匹配。

没想到这个办法。。