sgu123

。。。。费波拿起数前N项和。

/* *NAME:sum *LANG:C++ *Source:sgu123 */#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <cmath>#include <cctype>#include <string>#include <vector>using namespace std;int k;typedef int digit;class bigNum{private:    vector <digit> a;    int n;public:    bigNum(){ //构造函数 n=0;    }    int make (string c){          //将字符数组转化为向量 int l=c.size();a.resize(l);n=l;for (int i=0;i<l;++i){    a[i]=c[l-i-1]-'0';}--l;while (l>0 && a[l]==0) --l;n=l+1;return l+1;    }    void pout(){                    //输出 for (int i=n-1;i>-1;--i)    cout<<a[i];cout<<endl;    }    friend bigNum operator+(bigNum &a,bigNum &b){   //友元类型 重载+ bigNum r;int m=a.n>b.n?a.n:b.n;r.n=m;r.a.resize(m+10);for (int i=0;i<m;++i){    if (a.n>i) r.a[i]+=a.a[i];    if (b.n>i) r.a[i]+=b.a[i];    r.a[i+1]+=r.a[i]/10;    r.a[i]%=10;}++r.n;while (r.n>0 && r.a[r.n]==0) --r.n;++r.n;return r;    }    friend bigNum operator -(bigNum &a,bigNum &b){ //默认传入a>b 重载- bigNum r=a;int m=r.n;for (int i=0;i<m;++i){    if (b.n>i) r.a[i]-=b.a[i];int j=i;    while (r.a[j]<0){r.a[j]+=10;--r.a[j+1];    }}--m;while (m>0 && r.a[m]==0) --m;r.n=m+1;return r;    }    friend bool operator >(bigNum &a,bigNum &b){ //重载> 比较大小 if (a.n>b.n) return 1;if (a.n<b.n) return 0;for (int i=a.n-1;i>=0;--i){    if (a.a[i]>b.a[i]) return 1;    if (a.a[i]<b.a[i]) return 0;}return 0;    }    friend bool operator <(bigNum &a,bigNum &b){if (a.n<b.n) return 1;if (a.n>b.n) return 0;for (int i=a.n-1;i>=0;--i){    if (a.a[i]>b.a[i]) return 0;    if (a.a[i]<b.a[i]) return 1;}return 0;    }    friend bool operator ==(bigNum &a,bigNum &b){   //重载== if (a.n!=b.n) return 0;for (int i=0;i<a.n;++i)    if (a.a[i]!=b.a[i]) return 0;return 1;    }    friend bigNum operator * (bigNum &a,int b){     //重载* 高精度*低精度 bigNum r=a;r.a.resize(r.n+100);int m=r.n;for (int i=0;i<m;++i)    r.a[i]*=b;for (int i=0;i<m;++i){    r.a[i+1]+=r.a[i]/10;    r.a[i]%=10;}while (r.a[m]>=10) {r.a[m+1]+=r.a[m]/10;r.a[m++]%=10;}//while (m>0 && r.a[m]==0) --m;r.n=m+1;while (r.a[r.n-1]==0) --r.n;return r;    }    friend bigNum operator << (bigNum &a,int b){    //重载左移运算符，扩大10倍 bigNum r;r.a.resize(a.n+b);for (int i=0;i<a.n;++i)    r.a[i+b]=a.a[i];r.n=a.n+b;return r;    }    friend bigNum operator * (bigNum &a,bigNum &b){  //重载* 高精度*高精度 bigNum r,temp;r.a.resize(a.n+b.n);int k;for (int i=0;i<a.n;++i){    if (b.n<=i) continue;    temp=a*b.a[i];    temp=temp<<i;    r=r+temp;}r.n=a.n+b.n-1;for (int i=0;i<r.n;++i){    r.a[i+1]+=r.a[i]/10;    r.a[i]%=10;}while (r.n>0 && r.a[r.n]==0) --r.n;++r.n;return r;    }};int main(){    cin >> k;    bigNum sum,a,b,c;    a.make("1");b.make("1");sum.make("2");    if (k==1) {cout << 1 << endl;return 0;}    if (k==2) {cout << 2 << endl;return 0;}    for (int i=3;i<=k;++i){c=a+b;a=b;b=c;sum=sum+c;    }    sum.pout();    return 0;}