高精度/sgu112 a^b - b^a

题意

　　给出一个a一个b，求a^b - b^a

分析

　　高精度不解释

　　需要写三个高精度：

　　　　mult-计算乘法

　　　　compare-比较两个数的大小

　　　　minus-计算减法

Accepted Code

 1 {

 2     PROBLEM:SGU112

 3     AUTHER:Rinyo

 4     MEMO:高精度 模拟

 5 }

 6 Program sgu112;

 7 Type

 8   Rec = REcord

 9     len:Longint;

10     a:Array[0..1130]Of Longint;

11   End;

12 Var

13   a,b,aa,bb,i:Longint;

14   flag:Boolean;

15   aaa,bbb:REc;

16 Procedure mult(var a:Rec;k:Longint);

17 Var

18   i:Longint;

19 Begin

20   For i:=1 To a.len Do a.a[i]:=a.a[i]*k;

21   For i:=1 To a.len-1 Do Begin

22     Inc(a.a[i+1],a.a[i] Div 10);

23     a.a[i]:=a.a[i] Mod 10;

24   End;

25   i:=a.len;

26   While a.a[i]>9 Do Begin

27     Inc(a.a[i+1],a.a[i] Div 10);

28     a.a[i]:=a.a[i] Mod 10;

29     Inc(i);

30   End;

31   a.len:=i;

32 End;

33 Function compare(a,b:REc):Boolean;

34 Var

35   i:Longint;

36 Begin

37   If a.len<>b.len Then Begin

38     compare:=a.len>b.len;

39     Exit;

40   End Else

41   Begin

42     compare:=true;

43     For i:=a.len Downto 1 Do

44       If a.a[i]<>b.a[i] Then Begin

45         compare:=a.a[i]>b.a[i];

46         Exit;

47       End;

48   End;

49 End;

50 

51 Function minus(a,b:Rec):Rec;

52 Var

53   i:Longint;

54 Begin

55   For i:=1 To a.len Do Begin

56     a.a[i]:=a.a[i]-b.a[i];

57     If a.a[i]<0 Then Begin

58       Inc(a.a[i],10);

59       Dec(a.a[i+1]);

60     End;

61   End;

62   i:=a.len;

63   While (a.a[i]=0) And (i>1) Do Dec(i);

64   a.len:=i;

65   minus:=a;

66 End;

67 

68 Begin

69   ReadLn(a,b);

70   aa:=a;bb:=b;

71   aaa.len:=0;bbb.len:=0;

72   WHile aa>0 Do Begin

73     Inc(aaa.len);

74     aaa.a[aaa.len]:=aa Mod 10;

75     aa:=aa Div 10;

76   End;

77   While bb>0 Do Begin

78     Inc(bbb.len);

79     bbb.a[bbb.len]:=bb Mod 10;

80     bb:=bb Div 10;

81   End;

82   For i:=2 To b Do mult(aaa,a);

83   For i:=2 To a Do mult(bbb,b);

84   flag:=compare(aaa,bbb);

85   If flag Then aaa:=minus(aaa,bbb)

86           Else Begin

87             Write('-');

88             aaa:=minus(bbb,aaa);

89           End;

90   For i:=aaa.len Downto 1 Do Write(aaa.a[i]);

91   WriteLn;

92 End.