VF3用c语言实现
时间: 2023-10-22 08:06:26 浏览: 35
VF3是一种用于解决子图同构问题的算法。由于其效率高、实现简单,因此被广泛应用于图像识别、化学分子结构比对等领域。以下是一个用C语言实现的VF3算法的示例代码:
```
#include <stdio.h>
#include <stdlib.h>
#define MAXN 1000
#define MAXM 100000
int n1, n2, m1, m2, m;
int head1[MAXN], head2[MAXN], to1[MAXM], to2[MAXM], nxt1[MAXM], nxt2[MAXM];
int match[MAXN], f[MAXN], g[MAXN], stk[MAXN];
int cnt;
void add_edge(int head[], int to[], int nxt[], int u, int v)
{
to[cnt] = v, nxt[cnt] = head[u], head[u] = cnt++;
}
int dfs(int p, int q, int depth)
{
if (depth > n2)
return 1;
int u = to2[p];
for (int i = head1[u]; i != -1; i = nxt1[i]) {
int v = to1[i];
if (f[v] == q) {
f[v] = 0;
if (dfs(match[v], q, depth + 1)) {
match[v] = u;
return 1;
}
f[v] = q;
}
}
return 0;
}
void vf3(int depth)
{
if (depth > n1)
return;
int min_deg = n2 + 1, u = 0;
for (int i = 0; i < n1; i++) {
if (!g[i]) {
int deg = 0;
for (int j = head1[i]; j != -1; j = nxt1[j]) {
int v = to1[j];
if (!g[v])
deg++;
}
if (deg < min_deg) {
min_deg = deg;
u = i;
}
}
}
if (min_deg == n2 + 1)
return;
for (int i = head1[u]; i != -1; i = nxt1[i]) {
int v = to1[i];
if (!g[v]) {
g[v] = 1;
for (int j = head2[match[v]]; j != -1; j = nxt2[j]) {
int w = to2[j];
if (f[w] && dfs(head2[match[v]], f[w], 1)) {
match[v] = w;
break;
}
}
vf3(depth + 1);
g[v] = 0;
match[v] = -1;
for (int j = 0; j < cnt; j += 2) {
if (to1[j] == u && to2[j + 1] == v)
match[v] = to2[j];
}
}
}
}
int main()
{
scanf("%d%d%d", &n1, &m1, &n2);
for (int i = 0; i < n1; i++)
head1[i] = -1;
for (int i = 0; i < n2; i++)
head2[i] = -1;
cnt = 0;
for (int i = 0; i < m1; i++) {
int u, v;
scanf("%d%d", &u, &v);
add_edge(head1, to1, nxt1, u, v);
}
scanf("%d", &m2);
for (int i = 0; i < m2; i++) {
int u, v;
scanf("%d%d", &u, &v);
add_edge(head2, to2, nxt2, u, v);
}
for (int i = 0; i < n1; i++)
match[i] = -1;
for (int i = 0; i < n2; i++)
f[i] = i + 1;
vf3(1);
int ans = 0;
for (int i = 0; i < n1; i++) {
if (match[i] != -1) {
ans++;
stk[match[i]] = i;
}
}
printf("%d\n", ans);
for (int i = 0; i < n2; i++) {
if (stk[i])
printf("%d %d\n", stk[i], i);
}
return 0;
}
```
以上代码实现了VF3算法的主要部分,输入的格式为:
```
n1 m1 n2
u1 v1
u2 v2
...
m2
u1 v1
u2 v2
...
```
其中n1表示第一个图的节点数,m1表示第一个图的边数,n2表示第二个图的节点数,m2表示第二个图的边数。接下来m1行每行两个整数表示第一个图的一条边。接下来m2行每行两个整数表示第二个图的一条边。输出格式为:
```
k
u1 v1
u2 v2
...
```
其中k表示匹配的边数,接下来k行每行两个整数表示匹配的边。