POJ1001 -- A-B Problem

 

A-B Problem

 

Description
Calculate A-B

Input
Two integer a and b(-10^100 < a,b < 10^100)

Output
Output a-b

Sample Input

1 2

Sample Output

-1

Source

BUPT Online Judge

 

 

解：

过程很简单，主要是对大数运算的处理。在此运算只涉及加减法，相对容易。

当年自己用100+位的字符串表示大数。

按a和b的符号（即判断是否为负数），将运算分成四类进行处理。

 

如果用java，直接用BigDemical类实现即可，是最简单的方法。

 

#include <stdio.h>#include <string.h>void plus(char num1[101], char num2[101], int len1, int len2){ int carry = 0; int i; for (i = 1; i <= len2; i++) { num1[len1 - i] = num1[len1 - i] + num2[len2 - i] + carry - '0'; carry = 0; if (num1[len1 - i] > '9') { num1[len1 - i] = num1[len1 - i] - 10; carry = 1; } } for (; i <= len1; i++) { num1[len1 - i] = num1[len1 - i] + carry ; carry = 0; if (num1[len1 - i] > '9') { num1[len1 - i] = num1[len1 - i] - 10; carry = 1; } } i = 0; if (carry == 1) printf("1"); else { while (num1[i] == '0') { i++; } } while (num1[i] != '/0') { printf("%c", num1[i]); i++; } printf("/n");}void minus(char num1[101], char num2[101], int len1, int len2){ int carry = 0; int i; for (i = 1; i <= len2; i++) { num1[len1 - i] = num1[len1 - i] + '0' - num2[len2 - i] + carry ; carry = 0; if (num1[len1 - i] < '0') { num1[len1 - i] = num1[len1 - i] + 10; carry = -1; } } for (; i <= len1; i++) { num1[len1 - i] = num1[len1 - i] + carry ; carry = 0; if (num1[len1 - i] < '0') { num1[len1 - i] = num1[len1 - i] + 10; carry = -1; } } i = 0; while (num1[i] == '0') { i++; } while (num1[i] != '/0') { printf("%c", num1[i]); i++; } printf("/n");}void ABS(char num[101]){ int i; for (i = 1; num[i] != '/0'; i++) { num[i - 1] = num[i]; } num[i - 1] = '/0';}main(){ char a[101] = {'/0'}, b[101] = {'/0'}; int la, lb; scanf("%s%s", a, b); if (strcmp(a, b) == 0) { printf("0/n"); system("pause"); return 0; } la = strlen(a); lb = strlen(b); if (a[0] == '-') { ABS(a); la = la - 1; if (b[0] == '-') { ABS(b); lb = lb - 1; if (la > lb || (la == lb && strcmp(a, b)>0)) { printf("-"); minus(a, b, la, lb); } else { minus(b, a, lb, la); } } else { printf("-"); if (la > lb || (la == lb && strcmp(a, b)>0)) plus(a, b, la, lb); else plus(b, a, lb, la); } } else { if (b[0] == '-') { ABS(b); lb = lb - 1; if (la > lb || (la == lb && strcmp(a, b)>0)) plus(a, b, la, lb); else plus(b, a, lb, la); } else { if (la > lb || (la == lb && strcmp(a, b)>0)) minus(a, b, la, lb); else { printf("-"); minus(b, a, lb, la); } } } system("pause"); return 0; }