Submission #386477

#	Time	Username	Problem	Language	Result	Execution time	Memory
386477		kostia244	Islands (IOI08_islands)	C++17	61 / 100	290 ms	98284 KiB

islands

#include<bits/stdc++.h>
#define next uwuwuwuwu
using namespace std;
using ll = long long;
const int maxn = 1e6 + 6;
const ll inf = (1ll<<50);
int n;
int up[maxn];
ll dp[maxn], dep[maxn];
int tmp[maxn], tmp2[maxn], sz = 0, offset = 0, tsz = 0;
bitset<maxn> vis;

int link[maxn], next[maxn];
__attribute__(( always_inline)) inline void add_edge(int v, int ch) {
    next[ch] = link[v];
    link[v] = ch;
}

ll ans;

void dfs(int v) {
    #define u link[v]
    for(dp[v] = 0; u; u = next[u]) {
        dep[u] = dep[v] + up[u];
        dfs(u);
        ans = max(ans, dep[u] + dp[v] + dp[u] + up[u]);
        dp[v] = max(dp[v], dp[u] + up[u]);
    }
    #undef u
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin >> n;
    for(int i = 1; i <= n; i++) {
        cin >> up[i] >> dp[i];
    }
    for(int i = 1; i <= n; i++) if(!vis[i]) {
        sz = offset;
        int v = i;
        while(!vis[v]) {
            tmp[sz] = v;
            tmp2[sz++] = dp[v];
            vis[v] = 1;
            v = up[v];
        }
        reverse(tmp+offset, tmp+sz);
        reverse(tmp2+offset, tmp2+sz);
        while(sz>offset && tmp[sz-1] != v) sz--;
        for(int i = offset+1; i < sz; i++)
            swap(tmp2[i], tmp2[i-1]);
        if(sz<=offset) continue;//no new cycle
        tmp2[sz-1] *= -1;
        offset = sz;
    }
    vis = 0;
    for(int i = 0; i < sz; i++)
        vis[tmp[i]] = 1;
    for(int i = 1; i <= n; i++) if(!vis[i]) {
        add_edge(up[i], i);
    }
    for(int i = 0; i < n; i++)
        up[i] = dp[i];
    ll totalAns = 0, total = 0, pref = 0, A = -inf, B = -inf;
    for(int start = 0, end = 0; start < sz; start = ++end) {
        total = 0, pref = 0, A = -inf, B = -inf, ans = -inf;
        while(tmp2[end] >= 0) {
            total += tmp2[end];
            end++;
        }
        for(int i = start; i <= end; i++) {
            dfs(tmp[i]);
            ans = max(ans, A + pref + dp[tmp[i]]);
            ans = max(ans, B + dp[tmp[i]] + (total-pref) - tmp2[end]);
            A = max(A, dp[tmp[i]]-pref);
            B = max(B, dp[tmp[i]]+pref);
            pref += tmp2[i];
        }
        totalAns += ans;
    }
    cout << totalAns << '\n';
}

• Subtask 1: 24 / 33
• Subtask 2: 3 / 3
• Subtask 3: 4 / 4
• Subtask 4: 0 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10