368

# 题目

## Description

The fastfood chain McBurger owns several restaurants along a highway. Recently, they have decided to build several depots along the highway, each one located at a restaurant and supplying several of the restaurants with the needed ingredients. Naturally, these depots should be placed so that the average distance between a restaurant and its assigned depot is minimized. You are to write a program that computes the optimal positions and assignments of the depots.

To make this more precise, the management of McBurger has issued the following specification: You will be given the positions of n restaurants along the highway as n integers d1 < d2 < ... < dn (these are the distances measured from the company's headquarter, which happens to be at the same highway). Furthermore, a number k (k <= n) will be given, the number of depots to be built.

The k depots will be built at the locations of k different restaurants. Each restaurant will be assigned to the closest depot, from which it will then receive its supplies. To minimize shipping costs, the total distance sum, defined as

must be as small as possible.

Write a program that computes the positions of the k depots, such that the total distance sum is minimized.

## Input

The input file contains several descriptions of fastfood chains. Each description starts with a line containing the two integers n and k. n and k will satisfy 1 <= n <= 200, 1 <= k <= 30, k <= n. Following this will n lines containing one integer each, giving the positions di of the restaurants, ordered increasingly.

The input file will end with a case starting with n = k = 0. This case should not be processed.

## Output

For each chain, first output the number of the chain. Then output a line containing the total distance sum.

Output a blank line after each test case.

6 3
5
6
12
19
20
27
0 0

## Sample Output

Chain 1
Total distance sum = 8

# 题解

dp[i][j] 表示 i 个仓库,前 j 个饭店的最小值

k 为最右面的左半部分饭店时,恰好将中间距离给跳掉,因此为最优解

# 代码

/*
By:OhYee
Github:OhYee
Blog:http://www.oyohyee.com/
Email:oyohyee@oyohyee.com

かしこいかわいい？
エリーチカ！

*/
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <string>
#include <iostream>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <functional>
#include <bitset>
using namespace std;

const int INF = 0x7FFFFFFF / 2;

const int maxn = 205;
const int maxk = 35;

int kase = 1;

int restaurants[maxn];
int dp[maxk][maxn];
int Min[maxn][maxn];

bool Do() {
memset(dp,0,sizeof(dp));

int n,m;
cin >> n >> m;

if(n == 0 && m == 0)
return false;

for(int i = 1;i <= n;i++)
cin >> restaurants[i];

for(int i = 1;i <= n;i++) {
for(int j = i;j <= n;j++) {
if(i == j) {
Min[i][j] = 0;
} else {
int pos = restaurants[(i + j) / 2];
Min[i][j] = 0;
for(int k = i;k <= j;k++) {
Min[i][j] += abs(pos - restaurants[k]);
}
}
}
}

for(int i = 1;i <= m;i++)
if(i == 1) {
for(int j = 1;j <= n;j++)
dp[1][j] = Min[1][j];
} else {
for(int j = 1;j <= n;j++) {
dp[i][j] = INF;
for(int k = 1;k < j;k++) {
dp[i][j] = min(dp[i][j],dp[i - 1][k] + Min[k + 1][j]);
}
}
}
cout << "Chain "<<kase++ << endl <<"Total distance sum = "<<dp[m][n] << endl<<endl;

return true;
}
int vs_main() {
cin.tie(0);
std::cin.sync_with_stdio(false);

while(Do());
return 0;
}

• 点击查看/关闭被识别为广告的评论