A company has n employees numbered from 1 to n. Each employee either has no immediate manager or exactly one immediate manager, who is another employee with a different number. An employee A is said to be the superior of another employee B if at least one of the following is true:
- Employee A is the immediate manager of employee B
- Employee B has an immediate manager employee C such that employee A is the superior of employee C.
The company will not have a managerial cycle. That is, there will not exist an employee who is the superior of his/her own immediate manager.
Today the company is going to arrange a party. This involves dividing all n employees into several groups: every employee must belong to exactly one group. Furthermore, within any single group, there must not be two employees A and B such that A is the superior of B.
What is the minimum number of groups that must be formed?
The first line contains integer n (1 ≤ n ≤ 2000) — the number of employees.
The next n lines contain the integers pi (1 ≤ pi ≤ n or pi = -1). Every pi denotes the immediate manager for the i-th employee. If pi is -1, that means that the i-th employee does not have an immediate manager.
It is guaranteed, that no employee will be the immediate manager of him/herself (pi ≠ i). Also, there will be no managerial cycles.
Print a single integer denoting the minimum number of groups that will be formed in the party.
5 -1 1 2 1 -1
3
题意:给一片森林,求当中的树的最大深度。。
爆搜就可以
#include <iostream> #include <algorithm> #include <cstring> #include <cstdio> #include <cctype> #include <cstdlib> #include <set> #include <map> #include <vector> #include <string> #include <queue> #include <stack> #include <cmath> #define LL long long using namespace std; const int INF = 0x3f3f3f3f; int n,a[2010],ans,tem; void dfs(int u) { tem++; if(a[u]==-1) return ; dfs(a[u]); } void solve() { ans=-INF; for(int i=1;i<=n;i++) { tem=0; dfs(i); ans=max(ans,tem); } printf("%d ",ans); } int main() { while(~scanf("%d",&n)) { for(int i=1;i<=n;i++) scanf("%d",a+i); solve(); } return 0; }