Think:
1知识:并查集思想之森林的树
2反思:提高将问题建模到知识体系之中,且要敢于尝试
以下为Accepted代码——建议参考
#include <bits/stdc++.h>
using namespace std;
bool book[1998];
int main(){
int n, m, u, v, cnt;
while(scanf("%d %d", &n, &m) != EOF){
cnt = n;
memset(book, false, sizeof(book));
for(int i = 0; i < m; i++){
scanf("%d %d", &u, &v);
if(!book[v]){
book[v] = true;
cnt--;
}
}
printf("%d\n", cnt);
}
return 0;
}
/***************************************************
User name:
Result: Accepted
Take time: 0ms
Take Memory: 200KB
Submit time: 2017-07-14 08:57:39
****************************************************/
以下为Accepted代码——建议参考
#include <bits/stdc++.h>
using namespace std;
int n, f[1998];
void Init();
int get_f(int u);
void Merge(int u, int v);
int main(){
int m, i, cnt, u, v;
while(scanf("%d %d", &n, &m) != EOF){
Init();
cnt = 0;
for(i = 0; i < m; i++){
scanf("%d %d", &u, &v);
Merge(u, v);
}
for(i = 1; i <= n; i++){
if(f[i] == i)
cnt++;
}
printf("%d\n", cnt);
}
return 0;
}
void Init(){
for(int i = 1; i <= n; i++)
f[i] = i;
}
int get_f(int u){
if(f[u] == u){
return u;
}
else {
f[u] = get_f(f[u]);
return f[u];
}
}
void Merge(int u, int v){
int t1 = get_f(u);
int t2 = get_f(v);
f[t2] = t1;
}
/***************************************************
User name:
Result: Accepted
Take time: 0ms
Take Memory: 208KB
Submit time: 2017-07-14 09:07:21
****************************************************/