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Codeforces 755C：PolandBall and Forest（并查集）
Codeforces 755C：PolandBall and Forest（并查集）
时间：2021-07-01 10:21:17
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#include <cstdio>
2 #include <cstring>
3 #include <cmath>
4 #include <cstdlib>
5 #include <algorithm>
6 #include <
string>
7 #include <iostream>
8 #include <stack>
9 #include <map>
10 #include <queue>
11 #include <
set>
12 using namespace std;
13 typedef
long long LL;
14 #define N 100010
15 #define INF 0x3f3f3f3f
16 int fa[N], num[N];
17
18 int Find(
int x) {
19 if(x == fa[x])
return x;
20 return fa[x] =
Find(fa[x]);
21 }
22
23 void Merge(
int x,
int y) {
24 x = Find(x), y =
Find(y);
25 if(x == y)
return ;
26 fa[x] =
y;
27 }
28
29 int main()
30 {
31 int n;
32 scanf(
"%d", &
n);
33 for(
int i =
1; i <= n; i++) fa[i] =
i;
34 for(
int i =
1; i <= n; i++) scanf(
"%d", &
num[i]);
35 for(
int i =
1; i <= n; i++
) {
36 Merge(i, num[i]);
37 }
38 int ans =
0;
39 for(
int i =
1; i <= n; i++)
if(fa[i] == i) ans++
;
40 printf(
"%d\n", ans);
41 return 0;
42 }
Codeforces 755C：PolandBall and Forest（并查集）
标签：problems scanf tar 思路 inf merge color define 几分钟
