Python reverse string LCS solution (recursion+memoization)

#1 
def solve(self, A):
    import sys
    sys.setrecursionlimit(10**6)
    B=A[::-1]
    l=len(A)
    t=[[-1]*(l+1) for i in range(l+1)]
    def sol(i,j):
        if i==-1 or j==-1:
            return 0
        if t[i][j]!=-1:
            return t[i][j]
        if A[i]==B[j]:
            t[i][j]=1+sol(i-1,j-1)
        else:
            t[i][j]=max(sol(i-1,j),sol(i,j-1))
        return t[i][j]
    return sol(l-1,l-1)