hdu 1041 (OO approach, private constructor to prevent instantiation, sprintf) 分类： hdoj 2015-06-17 15:57 25人阅读 评论(0) 收藏

时间：2022-09-23 22:37:47

a problem where OO seems more natural to me, implementing a utility class not instantiable.

how to prevent instantiation, thanks to http://*.com/questions/10558393/prevent-instantiation-of-an-object-outside-its-factory-method/10558404#10558404

#include <cstdio>

#include <algorithm>

class CompTrans {

    CompTrans() { }

    static const unsigned NUMS_LEN=240000, MAX_NUM=1000, BASE=1000000000;

    static bool isinitialized;

    static char nums[NUMS_LEN];

    static char* pos[MAX_NUM+2];

public:

    static bool isinited() { return isinitialized; }

    static void init();

    static void printnth(unsigned n) { puts(pos[n]); }

    static unsigned getMAX_NUM() { return MAX_NUM; }

};

bool CompTrans::isinitialized=false;

char CompTrans::nums[];

char* CompTrans::pos[];

void CompTrans::init() {

    if(isinited()) return;

    int i,j,k;

    char *p=nums;

    const int NSIZE=40;

    unsigned n1[NSIZE]={0}, n2[NSIZE]={1}, n3[NSIZE]={0},tmp, *p1,*p2,*p3,*ptmp, carry;

    p1=n1,p2=n2,p3=n3;

    for(k=0, i=1;i<=MAX_NUM;++i) {

        pos[i]=p;

        p+=sprintf(p,"%u",p1[k]);

        for(j=k-1;j>=0;--j) p+=sprintf(p,"%09u",p1[j]);

        *p++=0;

        if(p2[k+1]!=0) ++k;

        for(carry=0, j=0;j<=k;++j) {

            tmp=carry+p2[j]+(p1[j]<<1);

            carry=tmp/BASE;

            p3[j]=tmp%BASE;

        }

        p3[j]=carry;

        ptmp=p1; p1=p2; p2=p3; p3=ptmp;

    }

    isinitialized=true;

}

int main() {

    //freopen("input.txt","r",stdin);

    int n;

    if(!CompTrans::isinited()) CompTrans::init();

    while(scanf("%d",&n)!=EOF && n<=CompTrans::getMAX_NUM()) {

        CompTrans::printnth(n);

    }

    return 0;

}

版权声明：本文为博主原创文章，未经博主允许不得转载。// p.s. If in any way improment can be achieved, better performance or whatever, it will be well-appreciated to let me know, thanks in advance.

相关文章