Permutation generation methods

heapperm.py

def swap(ar, i, j):
    tmp = ar[i]
    ar[i] = ar[j]
    ar[j] = tmp


def genheapperm(ar, n):
    if n == 1:
        print ar
        return
    for i in range(n):
        genperm(ar, n - 1)
        if n & 2 == 1:
          swap(ar, 0, n - 1)
        else:
          swap(ar, i, n - 1)
    genheapperm(ar, n - 1)


if __name__ == '__main__':
    ar = [1, 2, 3]
    genperm(ar, len(ar))

permutation.py

def swap(ar, i, j):
    tmp = ar[i]
    ar[i] = ar[j]
    ar[j] = tmp


def genperm(ar, n):
    if n == 1:
        print ar
        return
    for i in range(n):
        swap(ar, i, n - 1)
        genperm(ar, n - 1)
        swap(ar, i, n - 1)


if __name__ == '__main__':
    ar = [1, 2, 3]
    genperm(ar, len(ar))