AcWing 1977. 信息中继
原题链接
简单
作者:
生在逢时
,
2022-04-28 08:53:25
,
所有人可见
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阅读 212
并查集找到与0连通块元素个数
#include <iostream>
using namespace std;
const int N = 1010;
int p[N];
int siz[N];//维护集合元素个数
int find(int x)
{
if (x != p[x]) p[x] = find(p[x]);
return p[x];
}
int main()
{
int n;
cin >> n;
for (int i = 0; i <= n; i ++ )
p[i] = i, siz[i] = 1;
for (int i = 1; i <= n; i ++ )
{
int x;
cin >> x;
int pi = find(p[i]), px = find(p[x]);
p[p[i]] = px;
siz[px] += siz[pi];
}
cout << siz[0] - 1 << endl;//要减去 "0"本身
return 0;
}