poj1001 2010.2.25

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poj1001 2010.2.25

思路：

高精度乘法，忽略掉小数点，最后再点上，小数的位数，就是R的小数位数*n

#include <stdio.h>#include <string.h>#define N 10000#define M 15char s[M],mid[M];int num[N],ans[N],temp[N];int n,point,goal,ls,lnum,lans,ltemp;void change(){ls=strlen(s);ls--;int i;while (s[ls]=='0')ls--;int ls2=ls;point=0;while (s[ls2]!='.'){point++;ls2--;}lnum=0;memset(num,0,sizeof(num));for(i=ls;i>=0;i--)if (s[i]!='.'){lnum++;num[lnum]=s[i]-48;}goal=point*n;}void cal(){  lans=lnum;  int i,j,k;  memcpy(ans,num,sizeof(num));  for(k=1;k<n;k++)  {memset(temp,0,sizeof(temp));for(i=1;i<=lnum;i++)for(j=1;j<=lans;j++){temp[i+j-1]+=num[i]*ans[j];temp[i+j]+=temp[i+j-1]/10;temp[i+j-1]%=10;}ltemp=lans+lnum-1;while(temp[ltemp+1]){temp[ltemp+1]+=temp[ltemp]/10;temp[ltemp]%=10;ltemp++;}memcpy(ans,temp,sizeof(temp));lans=ltemp;  }//  for(i=lans;i>=1;i--)//  printf("%d",ans[i]);//  printf("\n");}void out(){int i;while (ans[lans]==0)lans--;if (lans<=goal){printf(".");for(i=goal;i>=1;i--)printf("%d",ans[i]);}else{for(i=lans;i>goal;i--)printf("%d",ans[i]);if (goal!=0) printf(".");for(i=goal;i>=1;i--)printf("%d",ans[i]);}printf("\n");}void main(){while (scanf("%s %d",s,&n)!=EOF){//printf("-----%s----%d-----\n",s,n);change();cal();out();}}

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