前一段时间花了几天看了一遍effective C++，感触很多，看起代码来总是觉得四处都在泄漏内存，于是就想上浙大oj玩，结果发现上不去了，伤心死，只好换到北大的OJ，发现pku的还是做得不错的，而且做得人更多，还有关于各个题目的讨论区，只是不喜欢题目后面的背景图片，太花了有点。结果今天又能上zju的oj了。。。
各个OJ的1001貌似都有点小陷阱，这道也是的，不过还算正常。
下面的程序可以AC，然后主要是为了练习copy ctor，运算符重载，虽然程序小，但是很多细节还是值得注意的，另外注意里面的加法只是为了在乘法中使用的，不是正常的加法，因为没有考虑小数点的对齐。想要用来直接做高精度数字类的话，需要改进运算符加号的内容。
和以前一样，重定向stdin是为了直接从文件输入测试数据，上OJ的时候去掉就好了。
#include<stdio.h> #include<string.h> #include<math.h> int n; class BigNum { public: BigNum(); BigNum(const char s[]); BigNum(const BigNum& x); void Print(); BigNum& operator=(const BigNum& lhs); private: int total; //how many digtal in total; int point; int m[300]; friend const BigNum operator+(const BigNum& lhs, const BigNum& rhs); friend const BigNum operator*(const BigNum& lhs, const BigNum& rhs); }; BigNum::BigNum(const char s[]) { int i; total = 0; point = 0; for(i=0;i<300;i++) { m[i] = 0; } int len = strlen(s); char front[6], back[6]; int fn=0, bn=0; bool flag = true, zeroflag = true; //div into two parts: front of point, back of point for(i=0;i<len;i++) { if(s[i]=='.') { flag = false; continue; } if(s[i]!='0') zeroflag = false; if(s[i]=='0' && zeroflag) { continue; } if(flag && !zeroflag) { front[fn++] = s[i] - 48; } else { back[bn++] = s[i] - 48; } } flag = true; for(i=bn-1;i>=0;i--) { if(back[i]=='0' && flag) continue; else { flag = false; m[++total] = back[i]; } } if(total!=0) point = total; flag = true; char tempstr[6]; int tn = 0; for(i=0;i<fn;i++) { if(front[i]=='0' && flag) continue; else { flag = false; tempstr[tn++] = front[i]; } } for(i=tn-1;i>=0;i--) { m[++total] = tempstr[i]; } if(total==0) { total = 1; m[1] = 0; } } BigNum::BigNum() { int i; total = 0; point = 0; for(i=0;i<300;i++) { m[i] = 0; } } BigNum::BigNum(const BigNum& x) { int i; total = x.total; point = x.point; for(i=0;i<300;i++) { m[i] = x.m[i]; } } void BigNum::Print() { int i, j,over=point-total; //when point>total if(over>0) { printf("."); for(i=0;i<over;i++) printf("0"); } //when ends with many zero for(j=1;j<=total;j++) { if(j>point) break; if(m[j]!=0) break; else continue; } for(i=total;i>=j;i--) { if(i==point) printf(".%d", m[i]); else printf("%d", m[i]); } } BigNum& BigNum::operator=(const BigNum& rhs) { int i; total = rhs.total; point = rhs.point; for(i=0;i<=total;i++) { m[i] = rhs.m[i]; } for(i=total+1;i<300;i++) m[i] = 0; return *this; } //only for mu, not really add const BigNum operator+(const BigNum& lhs, const BigNum& rhs) { BigNum t; int addto = 0; int i; t.total=lhs.total > rhs.total ? lhs.total : rhs.total; for(i=1;i<=t.total;i++) { t.m[i] = lhs.m[i] + rhs.m[i] + addto; if(t.m[i]>9) { t.m[i] = (lhs.m[i] + rhs.m[i] + addto) % 10; addto = 1; } else addto = 0; } if(addto>0) { t.m[++t.total] = addto; } return t; } const BigNum operator*(const BigNum& lhs, const BigNum& rhs) { BigNum a,b,c; int addto = 0,i,j,x; int maxt, temp; if(lhs.total>=rhs.total) { a = lhs; b = rhs; maxt = lhs.total; } else { a = rhs; b = lhs; maxt = rhs.total; } for(i=1;i<=b.total;i++) { addto = 0; BigNum *t = new BigNum; for(x=1;x<i;x++) { t->m[x] = 0; t->total++; } for(j=1;j<=a.total;j++) { temp = b.m[i] * a.m[j] + addto; t->m[j+x-1] = temp % 10; addto = (temp - t->m[j+x-1])/10; t->total++; } if(addto>0) { if(addto>9) { t->m[t->total+1] = addto%10; t->m[t->total+2] = (addto - t->m[t->total+1]) / 10; t->total += 2; } else { t->m[++t->total] = addto; } } c = c + (*t); delete t; } c.point = lhs.point + rhs.point; return c; } int main() { freopen("test.txt","r",stdin); char s[6]; int i; while(scanf("%s%d", s, &n)!=EOF) { if(n==0) { printf("0/n"); } else { BigNum *a = new BigNum(s); for(i = 0;i<5;i++) { s[i] = '0'; } s[5] = '1'; BigNum *b = new BigNum(s); for(i=1;i<=n;i++) { *b = (*b) * (*a); } b->Print(); printf("/n"); delete a, b; } } fclose(stdin); return 0; }