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大整数的＋－× /， 一般是将大整数看做一个字符串，每一位上的数字对应一个字符，然后对字符串进行处理。下面是进行大整数加法运算的例子，其他采用相同的方法可以实现。
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M h y M"H]F\www.linuxeden.com#include <stdio.h>
lS!Q2D$|I~www.linuxeden.com#include <stdlib.h>
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#define SIZE 5000c*l!?;B/@9h
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RIG JpLinux伊甸园论坛char *pa; // 字符串a首地址
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m [3?0f,dHchar *pb; // 字符串b首地址
a/_7w ie{Kchar *p_sum; // 结果字符串Av-BnK1Z(w
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int len_a = 0; // 字符串a的长度Linux伊甸园论坛 fFD-yT
int len_b = 0; // 字符串b的长度 K-qt"R D-i,g_
z/\E-PQ*Xwww.linuxeden.comvoid add();H$f NE\ N p i%b1g
{
/E(r F,{/g:lP int len; // 结果字符串的长度3?z*M n5Z.g+[
int carry = 0; // 是否有进位
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Z%s*Z"] char *start_a = pa+len_a-1; // 从a的个位开始'\!{
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char *start_b = pb+len_b-1; // 从b的个位开始www.linuxeden.com3yO:NF,c
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char *start_c; // 结果的个位Linux伊甸园论坛 q%|V^8z
5Q)q m+w S#D[ len = len_a>len_b?len_a:len_b;
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start_c = p_sum+len;
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[7S9I,Ggy*T while((start_a >= pa) && (start_b >= pb))+T Ao w!F]0T'i{
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u;?ALinux伊甸园论坛 if(*start_a + *start_b + carry - '0' <= '9')"oN2y1eW$YyA`
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+e+W1i)r5Y&[2V C *start_c = *start_a + *start_b + carry - '0';
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*start_c = *start_a + *start_b + carry - '9' - 1;
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start_b--;Linux伊甸园论坛J&E,?j.~ZF
start_c--;liU0Wm4iz
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if(*start_a + carry <= '9')www.linuxeden.com
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*start_c = *start_a + carry;
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*start_c = *start_a + carry - 10;(h M)\S&z `2Y1rQ
carry = 1;
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start_c--;
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*start_c = *start_b + carry;"xF } {z7Rxf-z
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carry = 0;
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T3pv~tR,G&d9b *start_c = *start_b + carry - 10;Linux伊甸园论坛2b#q/J _J@
carry = 1;*S2|4|6ho
}
#r%KI,DID H6y&]{ start_b--;
4yB5cR%P%o,vLinux伊甸园论坛 start_c--;(l"} }e5hW` }
}
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start_c = p_sum;
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start_c = p_sum + 1;
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printf("%s + %s = %s\n", pa, pb, start_c);
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rv GAPLinux伊甸园论坛 free(pa);:uZ8s9nl[#~
free(pb);Q6T/N3B0B$\/S2\Hd/^
free(p_sum);O)p%Y{*lY4c0f
}www.linuxeden.com Y.qE4b'goQ
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int main(void)
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char arr_in[SIZE];Linux伊甸园论坛}6I6C!P.l w;l
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printf("Please input a: ");
zyt|%Z:XLinux伊甸园论坛 scanf("%s", arr_in);{/E \{ Jq?
len_a = strlen(arr_in);www.linuxeden.comn g&aPG^[
pa = (char *)malloc((len_a + 1) * sizeof(char));
WP*?d)m3HSHT\w#Mwww.linuxeden.com strcpy(pa, arr_in);-V2|+v |4b
&gWj8H*[:Y printf("Please input b: ");VCD0g8d2WN&b+|J
scanf("%s", arr_in);
Cu;@ dAq)XK}8]? len_b = strlen(arr_in);
?*Y Y7i `fZ pb = (char *)malloc((len_b + 1) * sizeof(char));
[[$E$Izr strcpy(pb, arr_in); k^*VI~!SF
q(HX7L ] n0g add();
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return 0;&Y G,t;A0F
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[ 本帖最后由 xgf 于 2007-10-27 19:00 编辑 ]
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