如下内容，要求实现加、减运算，即能从键盘上输入两个大整数？该怎么解决？

Question

使用单链表实现不限大小的整数，每个结点存储一位数字。要求实现加、减运算，即能从键盘上输入两个大整数，比如：12345123451234512345和-11111111111111111111，则加的结果应为：01234012340123401234；减的结果应为：23456234562345623456。你的程序能运算并输出上述结果。要求：使用带表头结点的单链表实现，把符号位存在表头结点中。所以，你得先实现带表头结点的单链表，然后把每一个大数用一个链表来表示，再运算。

Answer 1

貌似写的太长了。。。= =另外就是没有完全测试，说不定某种输入情况下不对了，如果不对请告诉我～#include <stdio.h>#include <stdlib.h>#include <ctype.h>#define POS 0#define NEG 1typedef struct _node {int value;struct _node *next;} list_node, *integer;int greater(integer x, integer y) {int ax = abs(x->value), ay = abs(y->value);if (ax > ay) return 1;if (ax < ay) return 0;int res;list_node *nx = x->next, *ny = y->next;while (nx != 0) {if (nx->value > ny->value) res = 1;else if (nx->value < ny->value) res = 0;nx = nx->next;ny = ny->next;}return res;}int is_zero(integer n) {return n->value == 1 && n->next->value == 0;}void free_node_list(list_node *start) {list_node *node;while (start) {node = start;start = start->next;free(node);}}void free_node(list_node *node) {free(node);}list_node * make_node(int value) {list_node *node = (list_node *) malloc(sizeof(list_node));node->value = value;node->next = 0;return node;}integer negate(integer n) {list_node *new_header;if (is_zero(n))new_header = make_node(0);elsenew_header = make_node(-(n->value));new_header->next = n->next;return new_header;}void mutable_negate(integer n) {if (is_zero(n))return;n->value = -(n->value);}void insert_after(list_node *pos, list_node *new_node) {list_node *temp_node = pos->next;new_node->next = temp_node;pos->next = new_node;}list_node * add_node(list_node *pos, int value) {list_node *node = make_node(value);pos->next = node;return node;}void trim_trailing_zeros(integer i, int sign) {list_node *start, *last = i, *node;for (node = i->next; node != 0; node = node->next)if (node->value != 0)last = node;start = last->next;last->next = 0;while (start) {node = start;start = start->next;-- i->value;free(node);}if (i->value == 0) {i->next = make_node(0);i->value = 1;return;}if (sign == NEG) {i->value = -i->value;}}integer do_add(integer x, integer y) {list_node *header = make_node(x->value);list_node *nx = x->next, *ny = y->next, *last = header;int sum, carry = 0;while (ny != 0) {sum = nx->value + ny->value + carry;if (sum >= 10) {sum -= 10;carry = 1;} else {carry = 0;}last = add_node(last, sum);nx = nx->next;ny = ny->next;}while (nx != 0) {sum = nx->value + carry;if (sum >= 10) {sum -= 10;carry = 1;} else {carry = 0;}last = add_node(last, sum);nx = nx->next;}if (carry != 0) {add_node(last, 1);++header->value;}return header;}integer do_subtract(integer x, integer y) {list_node *header = make_node(x->value);list_node *nx = x->next, *ny = y->next, *last = header;int diff, borrow = 0;while (ny != 0) {diff = nx->value - ny->value - borrow;if (diff < 0) {diff += 10;borrow = 1;} else {borrow = 0;}last = add_node(last, diff);nx = nx->next;ny = ny->next;}while (nx != 0) {diff = nx->value - borrow;if (diff < 0) {diff += 10;borrow = 1;} else {borrow = 0;}last = add_node(last, diff);nx = nx->next;}trim_trailing_zeros(header, POS);return header;}integer add_positive(integer x, integer y) {if (greater(x, y)) return do_add(x, y);else return do_add(y, x);}integer subtract_positive(integer x, integer y) {if (greater(x, y)) return do_subtract(x, y);else {integer res = do_subtract(y, x);mutable_negate(res);return res;}}integer add(integer x, integer y) {if (x->value > 0) {if (y->value > 0) return add_positive(x, y);else {integer ny = negate(y);integer res = subtract_positive(x, ny);free_node(ny);return res;}} else {if (y->value > 0) {integer nx = negate(x);integer res = subtract_positive(y, nx);free_node(nx);return res;}else {integer nx = negate(x), ny = negate(y);integer res = add_positive(nx, ny);mutable_negate(res);free_node(nx);free_node(ny);return res;}}}integer subtract(integer x, integer y) {if (x->value > 0) {if (y->value > 0) return subtract_positive(x, y);else {integer ny = negate(y);integer res = add_positive(x, ny);free_node(ny);return res;}} else {if (y->value > 0) {integer nx = negate(x);integer res = add_positive(nx, y);mutable_negate(res);free_node(nx);return res;} else {integer nx = negate(x), ny = negate(y);integer res = subtract_positive(ny, nx);free_node(nx);free_node(ny);return res;}}}integer read_integer() {list_node *header = make_node(0);int c, sign = 0;while (!isdigit((c = getchar()))) {if (c == '+') sign = POS;if (c == '-') sign = NEG;}do {insert_after(header, make_node(c - '0'));++header->value;} while (isdigit((c = getchar())));trim_trailing_zeros(header, sign);return header;}void print_integer(integer i) {list_node *node = i->next;if (i->value < 0) {printf("-");}int length = abs(i->value);char *string = (char *) malloc(length + 1) + length;*string = '\0';for ( ; node != 0; node = node->next)*--string = node->value + '0';printf("%s", string);free(string);}int main() {integer x, y, z, w;x = read_integer();y = read_integer();z = add(x, y);w = subtract(x, y);print_integer(x);printf(" + ");print_integer(y);printf(" = ");print_integer(z);printf("\n");print_integer(x);printf(" - ");print_integer(y);printf(" = ");print_integer(w);printf("\n");free_node_list(x);free_node_list(y);free_node_list(z);free_node_list(w);return 0;}