dashuchengfa.rar_DaShuChengFa_大数 string

#include<iostream> using namespace std; /*void Multiple(char A[], char B[], char C[]) { int TMP, In=0, LenA=-1, LenB=-1; while(A[++LenA] != '\0'); while(B[++LenB] != '\0'); int Index, Start = LenA + LenB - 1; for(int i=LenB-1; i>=0; i--) { Index = Start--; if(B[i]!= '0') { for(int In=0, j=LenA-1; j>=0; j--) { TMP = (C[Index]-'0') + (A[j]-'0') * (B[i] - '0') + In; C[Index--] = TMP % 10 + '0'; In = TMP / 10; } C[Index] = In + '0'; } } } int main(int argc, char* argv[]) { char A[] = "21839244444444448880088888889"; char B[] = "38888888888899999999999999988"; char C[sizeof(A) + sizeof(B) - 1]; for(int k=0; k<sizeof(C); k++) C[k] = '0'; C[sizeof(C)-1] = '\0'; Multiple(A, B, C); for(int i=0; C != '\0'; i++) printf("%c", C); } */ //void Multiple(char A[], char B[], char C[]) //{ // int i=0,j=0,k=0,lenA=strlen(A),lenB=strlen(B),lenC=strlen(C); // for(k=0;k<lenC;k++) // {} //} #include <iostream> #include <string> using namespace std; void main() { string num1,num2;//被乘数和乘数，考虑到大整数，用string装入 cout<<"please input number1 and number2:"<<endl; cin>>num1>>num2; const char *p1=num1.c_str(); //转为char * const char *p2=num2.c_str(); int length=strlen(p1)+strlen(p2); char *p=new char [length]; //结果放在字符数组中 int i,j; for(i=0;i<length;++i) { p[i]='0'; //初始化结果数组，开始全为'0',对应数字0 } p[i]='\0'; int carry=0; //进位初时设为0 for(i=strlen(p1)-1;i>=0;--i)//由于要求小端存储，这里是模拟 { carry=0; for(j=strlen(p2)-1;j>=0;--j) { carry+=(p1[i]-'0')*(p2[j]-'0')+(p[i+j+1]-'0'); p[i+j+1]=carry%10+'0'; carry/=10; } } cout<<"两数相乘的结果为："; for(i=0;i<strlen(p);++i) { if(p[i]=='0') //输出越过前面的0 { continue; } cout<<p[i]; } cout<<endl; delete [] p; }