3.2.6 Sweet Butter 香甜的黄油
时间: 1ms 内存:64M
描述:
农夫John发现做出全威斯康辛州最甜的黄油的方法:糖。把糖放在一片牧场上,他知道N(1<=N<=500)只奶牛会过来舔它,这样就能做出能卖好价钱的超甜黄油。当然,他将付出额外的费用在奶牛上。 农夫John很狡猾。像以前的Pavlov,他知道他可以训练这些奶牛,让它们在听到铃声时去一个特定的牧场。他打算将糖放在那里然后下午发出铃声,以至他可以在晚上挤奶。 农夫John知道每只奶牛都在各自喜欢的牧场(一个牧场不一定只有一头牛)。给出各头牛在的牧场和牧场间的路线,找出使所有牛到达的路程和最短的牧场(他将把糖放在那)
输入:
第一行: 三个数:奶牛数N,牧场数(2<=P<=800),牧场间道路数C(1<=C<=1450) 第二行到第N+1行: 1到N头奶牛所在的牧场号 第N+2行到第N+C+1行: 每行有三个数:相连的牧场A、B,两牧场间距离D(1<=D<=255),当然,连接是双向的
输出:
一行 输出奶牛必须行走的最小的距离和
示例输入:
3 4 5
2
3
4
1 2 1
1 3 5
2 3 7
2 4 3
3 4 5
/*
{样例图形
P2
P1 @--1--@ C1
\ |\
\ | \
5 7 3
\ | \
\| \ C3
C2 @--5--@
P3 P4
}
*/
示例输出:
8
/*{说明:
放在4号牧场最优
}*/
提示:
参考答案(内存最优[1328]):
/*
ID:zhaofuk1
PROG: butter
LANG: C++
*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <utility>
#include <vector>
using namespace std;
const int INF = (1<<29);
const int MAXN = 810;
int n, p, c, e, dMin;
int d[MAXN], isIn[MAXN];
bool done[MAXN];
int head[MAXN];
typedef struct{
int u, v, next, c;
}Edge;
Edge nEdge[3000];
typedef pair<int, int> pill;
priority_queue<pill, vector<pill>, greater<pill> > q;
void AddEdge(int u, int v, int c)
{
nEdge[e].u = u; nEdge[e].v = v; nEdge[e].c = c;
nEdge[e].next = head[u]; head[u] = e++;
}
void dijkstra(int s)
{
pill u;
int x, sum;
for(int i = 1; i <= p; i++) d[i] = (i == s) ? 0 : INF;
memset(done, 0, sizeof(done));
q.push(make_pair(d[s], s));
while(!q.empty()){
u = q.top(); q.pop();
x = u.second;
if(done[x]) continue;
done[x] = true;
for(int ee = head[x]; ee != -1; ee = nEdge[ee].next){
if(d[nEdge[ee].v] > d[x] + nEdge[ee].c){
d[nEdge[ee].v] = d[x] + nEdge[ee].c;
q.push(make_pair(d[nEdge[ee].v], nEdge[ee].v));
}
}
}
sum = 0;
for(int i = 1; i <= p; i++){
sum += d[i] * isIn[i];
}
//printf(" sum = %d dmin=%d\n", sum, dMin);
if(dMin > sum) dMin = sum;
}
int main()
{
int x, y, z;
//freopen("butter.in", "r", stdin);
//freopen("butter.out", "w", stdout);
scanf("%d %d %d", &n, &p, &c);
memset(isIn, 0, sizeof(isIn));
for(int i = 0; i < n; i++){
scanf("%d", &x);
isIn[x]++;
}
for(int i = 1; i <= p; i++) head[i] = -1;
e = 0;
for(int i = 0; i < c; i++){
scanf("%d %d %d", &x, &y, &z);
AddEdge(x, y, z);
AddEdge(y, x, z);
}
dMin = INF;
for(int i = 1; i <= p; i++){
dijkstra(i);
}
printf("%d\n", dMin);
return 0;
}
参考答案(时间最优[608]):
/*
ID:zhaofuk1
PROG: butter
LANG: C++
*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <utility>
#include <vector>
using namespace std;
const int INF = (1<<29);
const int MAXN = 810;
int n, p, c, e, dMin;
int d[MAXN], isIn[MAXN];
bool done[MAXN];
int head[MAXN];
typedef struct{
int u, v, next, c;
}Edge;
Edge nEdge[3000];
typedef pair<int, int> pill;
priority_queue<pill, vector<pill>, greater<pill> > q;
void AddEdge(int u, int v, int c)
{
nEdge[e].u = u; nEdge[e].v = v; nEdge[e].c = c;
nEdge[e].next = head[u]; head[u] = e++;
}
void dijkstra(int s)
{
pill u;
int x, sum;
for(int i = 1; i <= p; i++) d[i] = (i == s) ? 0 : INF;
memset(done, 0, sizeof(done));
q.push(make_pair(d[s], s));
while(!q.empty()){
u = q.top(); q.pop();
x = u.second;
if(done[x]) continue;
done[x] = true;
for(int ee = head[x]; ee != -1; ee = nEdge[ee].next){
if(d[nEdge[ee].v] > d[x] + nEdge[ee].c){
d[nEdge[ee].v] = d[x] + nEdge[ee].c;
q.push(make_pair(d[nEdge[ee].v], nEdge[ee].v));
}
}
}
sum = 0;
for(int i = 1; i <= p; i++){
sum += d[i] * isIn[i];
}
//printf(" sum = %d dmin=%d\n", sum, dMin);
if(dMin > sum) dMin = sum;
}
int main()
{
int x, y, z;
//freopen("butter.in", "r", stdin);
//freopen("butter.out", "w", stdout);
scanf("%d %d %d", &n, &p, &c);
memset(isIn, 0, sizeof(isIn));
for(int i = 0; i < n; i++){
scanf("%d", &x);
isIn[x]++;
}
for(int i = 1; i <= p; i++) head[i] = -1;
e = 0;
for(int i = 0; i < c; i++){
scanf("%d %d %d", &x, &y, &z);
AddEdge(x, y, z);
AddEdge(y, x, z);
}
dMin = INF;
for(int i = 1; i <= p; i++){
dijkstra(i);
}
printf("%d\n", dMin);
return 0;
}
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