#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 10;
int n, a[N], f[N];
vector<int> g[N];
int dfn[N], dfc;
int d[N];
void dfs (int u) {
dfn[++ dfc] = u;
for (int & v : g[u]) {
d[v] = d[u] + 1;
dfs(v);
}
}
int dp[N];
int cal (int val) {
int ret = 0;
for (int i = 0; i <= n; i ++)
dp[i] = d[i];
for (int i = n; i >= 1; i --) {
int u = dfn[i];
if (dp[u] - d[u] == val || i == 1) {
ret ++;
dp[u] = -1;
}
dp[f[u]] = max(dp[f[u]], dp[u]);
}
return ret;
}
int nxt[N]; // nxt[i] : when k >= nxt[i], answer <= i
void solve (int st, int en, int l, int r) {
if (st > en || l > r) return;
if (l == r) {
for (int i = st; i <= en; i ++)
nxt[i] = l;
return;
}
int md = (st + en) >> 1;
nxt[md] = cal(md);
solve(st, md - 1, nxt[md], r);
solve(md + 1, en, l, nxt[md]);
}
int main (void) {
while (~scanf("%d", &n)) {
dfc = 0;
for (int i = 1; i <= n; i ++)
g[i].clear();
for (int i = 2; i <= n; i ++) {
scanf("%d", f + i);
g[f[i]].push_back(i);
}
dfs(1);
int m = 0;
for (int i = 1; i <= n; i ++)
m = max(m, d[i]);
solve(0, m, 1, n);
long long ans = 0;
for (int i = 1; i <= m; i ++)
ans += 1ll * i * (nxt[i - 1] - nxt[i]);
printf("%lld\n", ans);
}
}
知识点总结:STL****:(vector),dfs(Depth-First-Search)、clear()、