ECNUOJ 2575 Separate Connections
Separate Connections
Time Limit:5000MS Memory Limit:65536KB
Total Submit:421 Accepted:41
Description
Partychen are analyzing a communications network with at most 18 nodes. Character in a matrix i,j (i,j both 0-based,as matrix[i][j]) denotes whether nodes i and j can communicate ('Y' for yes, 'N' for no). Assuming a node cannot communicate with two nodes at once, return the maximum number of nodes that can communicate simultaneously. If node i is communicating with node j then node j is communicating with node i.
Input
The first line of input gives the number of cases, N(1 ≤ N ≤ 100). N test cases follow.
In each test case,the first line is the number of nodes M(1 ≤ M ≤ 18),then there are a grid by M*M describled the matrix.
Output
For each test case , output the maximum number of nodes that can communicate simultaneously
Sample Input
2
5
NYYYY
YNNNN
YNNNN
YNNNN
YNNNN
5
NYYYY
YNNNN
YNNNY
YNNNY
YNYYN
Sample Output
2
4
Hint
The first test case:
All communications must occur with node 0. Since node 0 can only communicate with 1 node at a time, the output value is 2.
The second test case:
In this setup, we can let node 0 communicate with node 1, and node 3 communicate with node 4.
Source
解题:逼格很高啊!带花树模板题,可惜本人不会敲,只好找了份模板
#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
using namespace std;
const int N = ;
int belong[N];
int findb(int x) {
return belong[x] == x ? x : belong[x] = findb(belong[x]);
}
void unit(int a, int b) {
a = findb(a);
b = findb(b);
if (a != b) belong[a] = b;
} int n, match[N];
vector<int> e[N];
int Q[N], rear;
int nxt[N], mark[N], vis[N];
int LCA(int x, int y) {
static int t = ;
t++;
while (true) {
if (x != -) {
x = findb(x);
if (vis[x] == t) return x;
vis[x] = t;
if (match[x] != -) x = nxt[match[x]];
else x = -;
}
swap(x, y);
}
} void group(int a, int p) {
while (a != p) {
int b = match[a], c = nxt[b];
if (findb(c) != p) nxt[c] = b;
if (mark[b] == ) mark[Q[rear++] = b] = ;
if (mark[c] == ) mark[Q[rear++] = c] = ; unit(a, b);
unit(b, c);
a = c;
}
} // 增广
void aug(int s) {
for (int i = ; i < n; i++) // 每个阶段都要重新标记
nxt[i] = -, belong[i] = i, mark[i] = , vis[i] = -;
mark[s] = ;
Q[] = s;
rear = ;
for (int front = ; match[s] == - && front < rear; front++) {
int x = Q[front]; // 队列Q中的点都是S型的
for (int i = ; i < (int)e[x].size(); i++) {
int y = e[x][i];
if (match[x] == y) continue; // x与y已匹配,忽略
if (findb(x) == findb(y)) continue; // x与y同在一朵花,忽略
if (mark[y] == ) continue; // y是T型点,忽略
if (mark[y] == ) { // y是S型点,奇环缩点
int r = LCA(x, y); // r为从i和j到s的路径上的第一个公共节点
if (findb(x) != r) nxt[x] = y; // r和x不在同一个花朵,nxt标记花朵内路径
if (findb(y) != r) nxt[y] = x; // r和y不在同一个花朵,nxt标记花朵内路径 // 将整个r -- x - y --- r的奇环缩成点,r作为这个环的标记节点,相当于论文中的超级节点
group(x, r); // 缩路径r --- x为点
group(y, r); // 缩路径r --- y为点
} else if (match[y] == -) { // y自由,可以增广,R12规则处理
nxt[y] = x;
for (int u = y; u != -; ) { // 交叉链取反
int v = nxt[u];
int mv = match[v];
match[v] = u, match[u] = v;
u = mv;
}
break; // 搜索成功,退出循环将进入下一阶段
} else { // 当前搜索的交叉链+y+match[y]形成新的交叉链,将match[y]加入队列作为待搜节点
nxt[y] = x;
mark[Q[rear++] = match[y]] = ; // match[y]也是S型的
mark[y] = ; // y标记成T型
}
}
}
} bool g[N][N];
char mp[N][N];
int main() {
int kase;
scanf("%d",&kase);
while(kase--) {
scanf("%d", &n);
for (int i = ; i < n; i++)
for (int j = ; j < n; j++) g[i][j] = false;
for(int i = ; i < n; ++i) e[i].clear();
for(int i = ; i < n; ++i){
scanf("%s",mp[i]);
for(int j = ; j < n; ++j){
if(mp[i][j] == 'Y'){
e[i].push_back(j);
e[j].push_back(i);
g[i][j] = g[j][i] = true;
}
}
}
for (int i = ; i < n; i++) match[i] = -;
for (int i = ; i < n; i++) if (match[i] == -) aug(i);
int tot = ;
for (int i = ; i < n; i++) if (match[i] != -) tot++;
printf("%d\n", tot);
}
return ;
}
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