zoj 3537 Cake （区间DP x 最优三角形剖分）

// 第一层 loop 枚举长度
for (int len = 1; len <= n; ++ len)
for (int i = 0; i + len - 1 < n; ++ i)

// 直接枚举端点
for (int j = 0; j < n; ++ j)
for (int i = j - 1; i >= 0; -- i)

struct Point {
double x, y;
Point(){};
Point(double x, double y):x(x),y(y){};

void read() {
scanf("%lf%lf", &x, &y);
}
};

typedef Point Vector;

Point operator - (const Point& a, const Point& b) {
return Point( a.x - b.x, a.y - b.y );
}

bool operator < (const Point& a, const Point& b) {
return a.x < b.x || (a.x == b.x && a.y < b.y);
}

double Cross(Vector A, Vector B) {
return A.x*B.y-A.y*B.x;
}

int ConvexHull(Point *p, int n, Point *ch) {
sort(p, p+n);
int m = 0;
for (int i=0;i<n;++i) {
while(m > 1 && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-2]) < 0)
--m;
ch[m++] = p[i];
}
int k = m;
for (int i=n-2;i>=0;--i) {
while(m > k && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-2]) < 0)
--m;
ch[m++] = p[i];
}
if (n > 1)
--m;
return m;
}

int n, p;
int dp

, cost

;
Point pts
, out
;

int calc(int lhs, int rhs) {
int x = abs(out[lhs].x + out[rhs].x), y = abs(out[lhs].y + out[rhs].y);
return x * y % p;
}

int main() {
while ( scanf("%d%d", &n, &p) != EOF ) {
rep(i, 0, n-1) pts[i].read();
int m = ConvexHull(pts, n, out);
if ( n != m ) {
puts("I can't cut.");
} else {
if ( n == 3 ) {
puts("0"); continue;
}
memset(cost, 0, sizeof(cost));
memset(dp, 0, sizeof(dp));
rep(i, 0, n-1) rep(j, i+2, n-1) {
if ( i == 0 && j == n - 1 ) continue;
cost[i][j] = cost[j][i] = calc(i, j);
}

for (int L = 3; L <= n; ++ L) {
for (int i = 0; i + L - 1 < n; ++ i) {
int j = i + L - 1;
dp[i][j] = INT_MAX;
for (int k = i + 1; k < j; ++ k) {
dp[i][j] = min ( dp[i][j], dp[i][k] + dp[k][j] + cost[i][k] + cost[j][k] );
}
}
}
printf("%d\n", dp[0][n-1]);
}
}
return 0;
}