C++三次样条插值代码

以下是C语言的三次样条插值代码：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define MAXN 1000

double x[MAXN], y[MAXN], a[MAXN], b[MAXN], c[MAXN], d[MAXN];
int n;

void input() {
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%lf%lf", &x[i], &y[i]);
    }
}

void solve() {
    double h[MAXN], alpha[MAXN], l[MAXN], mu[MAXN], z[MAXN];
    for (int i = 0; i < n - 1; i++) {
        h[i] = x[i + 1] - x[i];
    }
    for (int i = 1; i < n - 1; i++) {
        alpha[i] = 3 * (y[i + 1] - y[i]) / h[i] - 3 * (y[i] - y[i - 1]) / h[i - 1];
    }
    l[0] = 1;
    mu[0] = 0;
    z[0] = 0;
    for (int i = 1; i < n - 1; i++) {
        l[i] = 2 * (x[i + 1] - x[i - 1]) - h[i - 1] * mu[i - 1];
        mu[i] = h[i] / l[i];
        z[i] = (alpha[i] - h[i - 1] * z[i - 1]) / l[i];
    }
    l[n - 1] = 1;
    z[n - 1] = 0;
    c[n - 1] = 0;
    for (int j = n - 2; j >= 0; j--) {
        c[j] = z[j] - mu[j] * c[j + 1];
        b[j] = (y[j + 1] - y[j]) / h[j] - h[j] * (c[j + 1] + 2 * c[j]) / 3;
        d[j] = (c[j + 1] - c[j]) / (3 * h[j]);
        a[j] = y[j];
    }
}

void output() {
    for (int i = 0; i < n - 1; i++) {
        printf("S%d(x) = ", i);
        if (fabs(d[i]) > 1e-6) {
            printf("%lf(x - %lf)^3 + ", d[i], x[i]);
        }
        if (fabs(c[i]) > 1e-6) {
            printf("%lf(x - %lf)^2 + ", c[i], x[i]);
        }
        if (fabs(b[i]) > 1e-6) {
            printf("%lf(x - %lf) + ", b[i], x[i]);
        }
        printf("%lf\n", a[i]);
    }
}

int main() {
    input();
    solve();
    output();
    return 0;
}

代码中，input函数用于读入数据；solve函数用于计算三次样条插值的系数；output函数用于输出结果。其中，a、b、c、d数组分别存储三次样条插值的系数。