HDU 3480. Division

Brief description:

略。)

Analysis:

老套路。。雖然題目保證 32-int。。。但是實際還是有一些危險的(?)。
。全程 LL 居然會 TLE。=_=)

//}/* .................................................................................................................................. */

const int N = int(1e4) + 9;
int _f[2][N], *f = _f[0], *ff = _f[1]; int A[N]; int q[N], cz, op;
int n, m;

#define k (-2*A[i])
#define x(j) (A[j+1])
#define y(j) (ff[j] + sqr(x(j)))
#define eval(j) (k*x(j) + y(j))

LL det(LL x1, LL y1, LL x2, LL y2){
    return x1*y2 - x2*y1;
}
int dett(int p0, int p1, int p2){
    LL t = det(x(p1)-x(p0), y(p1)-y(p0), x(p2)-x(p0), y(p2)-y(p0));
    return t < 0 ? -1 : t > 0;
}

int main(){

#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
#endif

    Rush{

        RD(n, m); REP_1(i, n) RD(A[i]); sort(A+1, A+n+1);

        REP_1(i, n) f[i] = sqr(A[i] - A[1]);

        DO(m-1){
            swap(f, ff); cz = 0, op = -1; REP_1(i, n){
                while (cz < op && dett(q[op-1], q[op], i) <= 0) --op; q[++op] = i;
                while (cz < op && eval(q[cz]) >= eval(q[cz+1])) ++cz; f[i] = sqr(A[i]) + eval(q[cz]);
            }
        }

        OT(f[n]);
    }
}

http://acm.hust.edu.cn/vjudge/problem/viewSource.action?id=2801201