利用lagrange插值法计算函数值

x: 10 15 20

y: 1 1.1761 1.3010

求f(13);

答案：

#include <stdio.h>

#include <stdlib.h>

void main( void )

{

int n;

float *x = NULL;

float *y = NULL;

float xFound;

float yGet = 0.0;

float yGetTemp = 1.0;

printf("请输入你要输入的n的个数:");

scanf("%d", &n);

printf("请输入已知x的值(如:10 29 23 ……): ");

x = (float *)malloc(sizeof(float) * n);

for (int client = 0; client < n; client++)

scanf("%f", (x + client));

printf("\n");

printf("请输入已知Y的值(如:23 23 23 ……): ");

y = (float *)malloc(sizeof(float) * n);

for (client = 0; client < n; client++)

scanf("%f", (y + client));

printf("\n请输入要求的x的值: ");

scanf("%f", &xFound);

int temp;

for (client = 0; client < n; client++)

{

for (temp = 0; temp < n; temp++)

{

if (temp == client)

continue;

else

yGetTemp *= ( (xFound - *(x + temp)) / ( *(x + client) - *(x + temp)));

}

yGet += (yGetTemp * (*(y + client)));

yGetTemp = 1.0;

}

printf("\nThe result is:%f\n", yGet);

}