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Link: http://codepad.org/cR4jr4Vp    [ raw code | output | fork ]

Python, pasted on Feb 28:
def get_next_perm(p):
    n = len(p)
    i = n - 1
    while (i - 1) >= 0 and p[i - 1] > p[i]:
        i -= 1
    if i == 0:
        return p
    
    # this lookup may be optimized
    j = n - 1
    while p[j] <= p[i - 1]:
        j -= 1

    p[i - 1], p[j] = p[j], p[i - 1]

    # reverse i..n-1
    k = n - 1
    while i < k:
        p[i], p[k] = p[k], p[i]
        i += 1
        k -= 1

    return p
  
def value(p):
    return "".join(p)

if __name__ == "__main__":

    perm = "1 2 3 4 5".split()
    print(value(perm))
    old = []
    
    while True:
        old = perm[:]
        perm = get_next_perm(perm)
        if perm < old:
            print("%d %d!" % (value(perm), value(old)))
            break
        elif perm == old:
            break
        print(value(perm))


Output:
12345
12354
12435
12453
12534
12543
13245
13254
13425
13452
13524
13542
14235
14253
14325
14352
14523
14532
15234
15243
15324
15342
15423
15432
21345
21354
21435
21453
21534
21543
23145
23154
23415
23451
23514
23541
24135
24153
24315
24351
24513
24531
25134
25143
25314
25341
25413
25431
31245
31254
31425
31452
31524
31542
32145
32154
32415
32451
32514
32541
34125
34152
34215
34251
34512
34521
35124
35142
35214
35241
35412
35421
41235
41253
41325
41352
41523
41532
42135
42153
42315
42351
42513
42531
43125
43152
43215
43251
43512
43521
45123
45132
45213
45231
45312
45321
51234
51243
51324
51342
51423
51432
52134
52143
52314
52341
52413
52431
53124
53142
53214
53241
53412
53421
54123
54132
54213
54231
54312
54321


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