#include <cstdlib> #include <cstdio> #include <vector> #include <map> #include <algorithm> using namespace std; void reverse(char*s) { if (s == NULL ) return; char *e = s + strlen(s) - 1; while (s < e) swap(*s, *e), s++, e--; } char* add(char* a, char* b) { if (a == NULL || b == NULL) return NULL; int la = strlen(a), lb = strlen(b); int lc = max(la, lb) + 2; char*c = new char[lc]; c[0] = '\0'; reverse(a); reverse(b); int carr = 0; int i = 0, t; while (i < la && i < lb) { t = a[i] - '0' + b[i] - '0' + carr; carr = t / 10; c[i] = (t % 10) + '0'; i++; } while (i < la) { t = a[i] - '0' + carr; carr = t / 10; c[i++] = (t % 10) + '0'; } while (i < lb) { t = b[i] - '0' + carr; carr = t / 10; c[i++] = (t % 10) + '0'; } if (carr != 0) c[i++] = '1'; c[i] = '\0'; reverse(a); reverse(b); reverse(c); return c; } int cmp(char *a, char *b) { int la = strlen(a), lb = strlen(b); if (la != lb) return la - lb; else { while (*a != '\0' && *a == *b) a++, b++; return *a - *b; } } char* minus(char *a, char *b) { if (a == NULL || b == NULL) return NULL; if (cmp(a, b) < 0) { char *c = minus(b, a); reverse(c); int l = strlen(c); c[l] = '-'; c[l+1] = '\0'; reverse(c); return c; } int la = strlen(a), lb = strlen(b); int lc = max(la, lb) + 2; char*c = new char[lc]; c[0] = '\0'; reverse(a); reverse(b); int carr = 0; int i = 0, t; while (i < la && i < lb) { t = a[i] - b[i] + carr; if (t < 0) carr = -1, t += 10; else carr = 0; c[i++] = t + '0'; } while (i < la) { t = a[i] + carr - '0'; if (t < 0) carr = -1, t += 10; else carr = 0; c[i++] = t + '0'; } while (--i > 0 && c[i] == '0') ; c[i+1] = '\0'; reverse(a); reverse(b); reverse(c); return c; } int main() { char a[] = "2223"; char b[] = "222999"; auto res = minus(a, b); return 0; }
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