标签:future output 子集 c++ deb put ddl equal main
As you could know there are no male planes nor female planes. However, each plane on Earth likes some other plane. There are n planes on Earth, numbered from 1 to n, and the plane with number i likes the plane with number fi, where 1 ≤ fi ≤ n and fi ≠ i.
We call a love triangle a situation in which plane A likes plane B, plane B likes plane C and plane C likes plane A. Find out if there is any love triangle on Earth.
The first line contains a single integer n (2 ≤ n ≤ 5000) — the number of planes.
The second line contains n integers f1, f2, ..., fn (1 ≤ fi ≤ n, fi ≠ i), meaning that the i-th plane likes the fi-th.
Output «YES» if there is a love triangle consisting of planes on Earth. Otherwise, output «NO».
You can output any letter in lower case or in upper case.
5
2 4 5 1 3
YES
5
5 5 5 5 1
NO
In first example plane 2 likes plane 4, plane 4 likes plane 1, plane 1 likes plane 2 and that is a love triangle.
In second example there are no love triangles.
是否存在三角关系,简单题。
1 #include <bits/stdc++.h> 2 #define ll long long 3 using namespace std; 4 const int N = 5e3+10; 5 int f[N]; 6 int main() { 7 int n; 8 cin >> n; 9 for(int i = 1; i <= n; i ++) cin >> f[i]; 10 for(int i = 1; i <= n; i ++) { 11 if(i == f[f[f[i]]]) return 0*printf("YES\n"); 12 } 13 printf("NO\n"); 14 return 0; 15 }
Codeforces Round #464 (Div. 2) ABCDE
标签:future output 子集 c++ deb put ddl equal main
原文地址:https://www.cnblogs.com/xingkongyihao/p/8955375.html