大数加减法
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1 #include <cstdio> 2 #include <cstring> 3 using namespace std; 4 #define MAX 10005 5 6 struct bigint 7 { 8 char num[MAX]; 9 int flag; // 1:positive -1:negative 10 int dgts; 11 bigint(void) 12 { 13 memset(num, ‘0‘, sizeof(num)); 14 } 15 }; 16 17 void BigIntTrans(char str[], bigint* a) //convert string to the structure of bigint 18 { 19 int i, k, len; 20 len = strlen(str); 21 a->flag = 1; 22 a->dgts = len; 23 k = 0; 24 for(i = len - 1; i >= 1; --i) 25 a->num[k++] = str[i]; 26 if(str[0] == ‘-‘) { 27 a->flag = -1; 28 --a->dgts; 29 } 30 else { 31 a->num[k++] = str[i]; 32 } 33 } 34 35 void BigIntPrint(bigint* a) 36 { 37 int i; 38 if(a->flag == -1) printf("-"); 39 if(a->dgts == 1 && a->num[0] == ‘0‘) { 40 printf("0\n"); 41 return; 42 } 43 i = a->dgts - 1; 44 while(a->num[i] == ‘0‘) 45 --i; 46 for( ; i >= 0; --i) { 47 printf("%c", a->num[i]); 48 } 49 printf("\n"); 50 } 51 52 void add(bigint* a, bigint* b, bigint* ans) 53 { 54 int i, c=0, len, tmp; 55 len = (a->dgts >= b->dgts? a->dgts:b->dgts); 56 for(i = 0; i < len; ++i) { 57 tmp = (a->num[i]-‘0‘) + (b->num[i]-‘0‘) + c; 58 if(tmp >= 10){ 59 c = 1; 60 ans->num[i] = (tmp % 10) + ‘0‘; 61 } 62 else { 63 c = 0; 64 ans->num[i] = tmp + ‘0‘; 65 } 66 } 67 if(c) { 68 ans->num[i] = ‘1‘; 69 ans->dgts = len + 1; 70 } 71 else ans->dgts = len; 72 if(a->flag + b->flag == 2) ans->flag = 1; 73 else ans->flag = -1; 74 } 75 76 void sub(bigint* a, bigint* b, bigint* ans) 77 { 78 int i, c=0, tmp; 79 for(i = 0; i < a->dgts; ++i) { 80 tmp = (a->num[i]-‘0‘) - (b->num[i]-‘0‘) - c; 81 if(tmp >= 0) { 82 ans->num[i] = tmp + ‘0‘; 83 c = 0; 84 } 85 else { 86 ans->num[i] = tmp + 10 + ‘0‘; 87 c = 1; 88 } 89 } 90 ans->dgts = a->dgts; 91 ans->flag = a->flag; 92 } 93 94 int cmpabs(bigint* a, bigint* b) 95 { 96 if(a->dgts > b->dgts) 97 return 1; 98 else if(a->dgts < b->dgts) 99 return 2; 100 else { 101 for(int i = a->dgts - 1; i >= 0; --i) { 102 if(a->num[i] > b->num[i]) return 1; 103 else if(a->num[i] < b->num[i]) return 2; 104 else continue; 105 } 106 return 0; 107 } 108 } 109 110 void BigIntAdd(bigint* a, bigint* b, bigint* ans) 111 { 112 int flag; 113 if(a->flag * b->flag == 1) 114 add(a, b, ans); 115 else if(a->flag * b->flag == -1) { 116 flag = cmpabs(a, b); 117 if(flag == 1) sub(a, b, ans); 118 else if(flag == 2) sub(b, a, ans); 119 else { 120 ans->dgts = 1; 121 ans->num[0] = ‘0‘; 122 ans->flag = 1; 123 } 124 } 125 126 } 127 128 char str1[MAX], str2[MAX]; 129 130 int main() 131 { 132 bigint a, b, ans; 133 scanf("%s%s", str1, str2); 134 BigIntTrans(str1, &a); 135 BigIntTrans(str2, &b); 136 sub(&a, &b, &ans); 137 BigIntPrint(&ans); 138 BigIntAdd(&a, &b, &ans); 139 BigIntPrint(&ans); 140 return 0; 141 }
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