HDU - 3516 Tree Construction

HDU - 3516

思路：

平行四边形不等式优化dp

：）

代码：

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize(4)
#include<bits/stdc++.h>
using namespace std;
#define y1 y11
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
#define LD long double
//#define mp make_pair
#define pb push_back
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pli pair<LL, int>
#define pii pair<int, int>
#define piii pair<int, pii>
#define pdd pair<long double, long double>
#define mem(a, b) memset(a, b, sizeof(a))
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//headconst int N = 1e3 + 5;
int dp[N][N], s[N][N], x[N], y[N], n;
int main() {while(~scanf("%d", &n)) {for (int i = 1; i <= n; ++i) scanf("%d %d", &x[i], &y[i]);for (int i = n; i >= 1; --i) {dp[i][i] = 0;s[i][i] = i;for (int j = i+1; j <= n; ++j) {dp[i][j] = 0x3f3f3f3f;for (int k = s[i][j-1]; k <= s[i+1][j]; ++k) {if(k+1 <= j && dp[i][k]+dp[k+1][j]+y[k]-y[j]+x[k+1]-x[i] < dp[i][j]) {dp[i][j] = dp[i][k]+dp[k+1][j]+y[k]-y[j]+x[k+1]-x[i];s[i][j] = k;}}}}printf("%d\n", dp[1][n]);}return 0;
}