You are given three sequences A, B and C. The length of the three sequences is m, n and m+n respectively. In other words, the length of C is the sum of the length of A and B. Design an algorithm to check if A and B can be merged into C such that the order of all the letters in A and B is preserved. Example 1: A=aabb, B=cba, C=acabbab, then your algorithm should return true.

Example 2: A=aabb, B=cba, C=aaabbbc, then your algorithm should return false.