http://poj.org/problem?id=3026
Time Limit:1000MS Memory Limit:65536KB 64bit IO Format:%I64d & %I64u
Description
Your task is to help the Borg (yes, really) by developing a program which helps the Borg to estimate the minimal cost of scanning a maze for the assimilation of aliens hiding in the maze, by moving in north, west, east, and south steps. The tricky thing is that the beginning of the search is conducted by a large group of over 100 individuals. Whenever an alien is assimilated, or at the beginning of the search, the group may split in two or more groups (but their consciousness is still collective.). The cost of searching a maze is definied as the total distance covered by all the groups involved in the search together. That is, if the original group walks five steps, then splits into two groups each walking three steps, the total distance is 11=5+3+3.
Input
Output
Sample Input
2
6 5
#####
#A#A##
# # A#
#S ##
#####
7 7
#####
#AAA###
# A#
# S ###
# #
#AAA###
#####
Sample Output
8
11
最小生成树问题,但较不同点的是没有给原图,所以要用BFS找各个字母之间的距离,即构成原图
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#include<ctype.h>
#include<queue>
#define INF 0x3f3f3f3f
#define max(a, b)(a > b ? a : b)
#define min(a, b)(a < b ? a : b)
#define N 110 using namespace std; struct node
{
int x, y, step;
}; int G[N][N], dist[N], p[N][N];//p记录字母的坐标
bool vis[N], use[N][N];
char maps[N][N];
int m, n, num;
int d[][] = {{, }, {, }, {-, }, {, -}}; void Init()
{
int i, j;
memset(p, , sizeof(p));
memset(vis, false, sizeof(vis));
for(i = ; i <= num ; i++)
{
for(j = ; j <= num ; j++)
{
if(i == j)
G[i][j] = ;
else
G[i][j] = G[j][i] = INF;
}
}
} int prim(int s)//最小生成树,求最小花费
{
int i, j, index, Min, ans = ;
for(i = ; i <= num ; i++)
dist[i] = G[s][i];
vis[s] = true;
for(i = ; i < num ; i++)
{
Min = INF;
for(j = ; j <= num ; j++)
{
if(!vis[j] && dist[j] < Min)
{
Min = dist[j];
index = j;
}
}
ans += Min;
vis[index] = true;
for(j = ; j <= num ; j++)
{
if(!vis[j] && dist[j] > G[index][j])
dist[j] = G[index][j];
}
}
return ans;
} void BFS(int x, int y)//广搜构建原图
{
queue<node>Q;
int i, a, b;
node now, next;
memset(use, false, sizeof(use));
now.x = x;
now.y = y;
now.step = ;
use[x][y] = true;
Q.push(now);
while(!Q.empty())
{
now = Q.front();
Q.pop();
if(p[now.x][now.y] > )//该点为字母
G[p[x][y]][p[now.x][now.y]] = now.step;
for(i = ; i < ; i++)
{
a = next.x = now.x + d[i][];
b = next.y = now.y + d[i][]; if(a >= && a < m && b >= && b < n && !use[a][b] && maps[a][b] != '#')
{
next.step = now.step + ;
use[a][b] = true;
Q.push(next); }
}
}
} int main()
{
int i, j, t;
scanf("%d", &t);
while(t--)
{
scanf("%d%d ", &n, &m);
Init();
num = ;
for(i = ; i < m ; i++)
{
for(j = ; j < n ; j++)
{
scanf("%c", &maps[i][j]);
}
getchar();
}
for(i = ; i < m ; i++)
{
for(j = ; j < n ; j++)
{
if(maps[i][j] == 'A' || maps[i][j] == 'S')
p[i][j] = ++num;//统计字母的个数,即要进入树的点的个数
}
}
for(i = ; i < m ; i++)
{
for(j = ; j < n ; j++)
if(p[i][j] > )
BFS(i, j);
}
printf("%d\n", prim());
}
return ;
}