#include<stdio.h>
#include<conio.h>
#include<random>
#include<windows.h>
#include<time.h>
#include<math.h>
double getSum1(double x_, int n_, double nums[]);
double getSum2(double x_, int n_, double nums[]);
clock_t time1;
clock_t time2;
clock_t time3;
int main() {
// 测试多项式的和
// f(x) = a1 + a2*x +a3*x^2 + ... + an*x^(n-1)
/*
srand(unsigned(time(NULL)));
int randomize(void);
int a = rand() % 50;
printf("a: %d\n", a);
*/
int n = 10;
double x = 3.1;
int run_Cycle = 1000000;
double nums[10] = {};
for (int i = 0; i < n; i++) {
nums[i] = (double)(rand() % 10);
//printf("number %d: %d\n", i, nums[i]);
}
time1 = clock();
double result1;
for (int i = 0; i < run_Cycle; i++) {
result1 = getSum1(x, n, nums);
}
time2 = clock();
printf("ticks1 %f\n", (double)(time2 - time1));
printf("function a takes %6.2e s, result = %f\n", (double)(time2-time1)/CLOCKS_PER_SEC/run_Cycle, result1);
double result2;
for (int i = 0; i < run_Cycle; i++) {
result2 = getSum2(x, n, nums);
}
time3 = clock();
printf("ticks2 %f\n", (double)(time3 - time2));
printf("function b takes %6.2e s, result = %f\n", (double)(time3 - time2)/CLOCKS_PER_SEC/run_Cycle, result2);
_getch();
return 0;
}
// 加号前各项相加
double getSum1(double x, int n, double nums[]) {
double sum = 0;
for (int i = 0; i < n; i++) {
sum += (pow(x, i) * nums[i]);
}
return sum;
}
// 提取公因式算法
double getSum2(double x, int n, double nums[]) {
double p = nums[n - 1];
for (int i = n - 2; i >= 0; i--) {
p = p * x + nums[i];
}
return p;
}