10252.common permutation

>> বুধবার, ১৮ নভেম্বর, ২০০৯

Given two strings of lowercase letters, a and b, print the longest string x of lowercase letters such that there is a permutation of x that is a subsequence of a and there is a permutation of x that is a subsequence of b.



Input
Input file contains several lines of input. Consecutive two lines make a set of input. That means in the input file line 1 and 2 is a set of input, line 3 and 4 is a set of input and so on. The first line of a pair contains a and the second contains b. Each string is on a separate line and consists of at most 1000 lowercase letters.

Output
For each set of input, output a line containing x. If several x satisfy the criteria above, choose the first one in alphabetical order.

Sample Input:

icky
pretty
women
walking
down
the
street
meningitis
frontal
yelp

verbatim
greater
prettywoman
walkingdown
inging
singing
ab
ba
ab
cd
cat
bat

Sample Output:

e
nw
et
nt

aert
anow
ggiinn
ab

at

!Be careful: here may be empty lines in the input.
Discussion:
You can use straightforward algorithm or the following:
1. First take two array A[],B[],sort two input by using qsort() function.
2. Each char of two string is convert into integer n then A[n]++ for A[] and B[n]++ for B[].
3. Then from i=97 to 122  a to z element of A[] & B[] check, if both have value greater than 0 then take m=min(A[i],B[i]). Convert I to char ch. Ch print m times
4. Print newline.
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