多项式计算

#include <stdio.h>#include <iostream>#include <time.h>using namespace std;#define N 1e8int fun1(int x)//i*x^i{    int sum = 0;    for (int i = 0; i < 10; i ++) {        sum = i * sum + i - 1;            }    return sum;}//f(x) = a0 + x * (a1 + x * (a2 + ...x * (an-1 + an * x)...)) 

int fun2(int x){    int sum = 0,temp = 1;    for (int i = 1; i < 10; i ++) {        temp = temp * x;        sum = sum + i * temp ;    }    return sum;}int main(){    int x;    cin >> x;    clock_t strat,end;    strat = clock();//记录从程序开始至今的clock tick</span></span>

    for (int i = 0; i < N;i ++)    {        fun1(x);            }   end = clock();    double d1 = (end - strat)/N;    printf("best : %6.5f\n",d1);    strat = clock();    for (int i = 0; i < N;i ++)    {        fun2(x);            }    end = clock();    double d2 = (end - strat)/N;   printf("%6.5f\n",d2);    return 0;}

输出：

5

0.02594

0.02917