from functools import cache

def isInterleave(u: str, v: str, t: str) -> bool:
    m, n, k = len(u), len(v), len(t)
    if m + n != t: return False
    
    @cache
    def memo(i, j, k):
        if k == 0:
            return i == 0 and j == 0

        if i > 0 and u[i - 1] == t[k - 1] and memo(i - 1, j, k - 1):
            return True
        if j > 0 and v[j - 1] == t[k - 1] and memo(i, j - 1, k - 1):
            return True

        return False

    return memo(m, n, k)