6來飛起

圖片的i=j？下面第二個應該為temp = temp / (xi - xj);

#include "cstdio"

const int MAXN = (int) 1e5 + 5;

struct point  {
    double x, y;
} list[MAXN];

int n, m;
double x;

double Lagrange( point *list, int qnum, double x )  {
    double rt = 0, tmp = 1.0;
    for(int i = 1; i <= qnum; rt += list[i].y * tmp, tmp = 1.0
 
, ++i)
        for(int j = 1; j <= qnum; ++j)
            if(i != j)
                tmp *= (x - list[j].x) / (list[i].x - list[j].x);
    return rt;
}

int main()  {
    scanf("%d", &n);
    for(int i = 1; i <= n; scanf("%lf%lf", &list[i].x, &list[i].y), ++i);
    scanf("%d", &m);
    while
 
( m-- )
        scanf("%lf", &x), printf("%lf\n", Lagrange(list, n, x));
}

感覺自己學了假的OI， 姚班大神虐蒟蒻~

大家都很強， 可與之共勉。

2017.3.18