#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 200010;
int n, m;
int h[N], e[N], ne[N], idx;
int color[N];
void add(int a, int b)
{
e[idx] = b, ne[idx] = h[a], h[a] = idx ++;
}
bool dfs(int u, int c)
{
color[u] = c;
for(int i = h[u]; i != -1; i = ne[i]){
int j = e[i];
if(!color[j]){
if(!dfs(j, 3-c))
return false;
}
else if(color[j] == c)
return false;
}
}
int main()
{
scanf("%d%d", &n, &m);
memset(h, -1, sizeof h);
while(m--){
int a, b;
scanf("%d%d", &a, &b);
add(a, b), add(b, a);
}
bool flag = true;
for(int i = 1; i <= n; i++)
if(!color[i]){
if(!dfs(i, 1)){
flag = false;
break;
}
}
if(flag)
puts("Yes");
else
puts("No");
return 0;
}
2、匈牙利算法
cpp复制代码
#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 510, M = 100010;
int n1, n2, m;
int h[N], e[N], ne[N], idx;
int match[N];
bool st[N];
void add(int a, int b)
{
e[idx] = b, ne[idx] = h[a], h[a] = idx ++;
}
bool find(int x)
{
for(int i = h[x]; i != -1; ne[i]){
int j = e[i];
if(!st[j]){
st[j] = true;
if(match[j] == 0 || find(match[j])){
match[j] = x;
return true;
}
}
}
return false;
}
int main()
{
scanf("%d%d%d", &n1, &n2, &m);
memset(h, -1, sizeof h);
while(m--){
int a, b;
scanf("%d%d", &a, &b);
add(a, b);
}
int res = 0;
for(int i = 1; i <= n1; i++){
memset(st, false, sizeof st);
if(find(i))
res ++;
}
printf("%d\n", res);
return 0;
}