Submission #889513

#	Time	Username	Problem	Language	Result	Execution time	Memory
889513		Macker	Islands (IOI08_islands)	C++17	6 / 100	233 ms	131072 KiB

islands

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define all(v) v.begin(), v.end()

struct node{
    vector<pair<int, int>> adj = {};
    vector<int> binJmp;
    vector<int> binDp;
    vector<int> binSum;
    bool isCyc = 0;
    int mxd = 0;
    int vis = 0;
};

vector<node> v;
vector<vector<int>> cycles;

int precDfs(int a, int p){
    v[a].vis = 1;
    int cyc = -1;
    for (auto &i : v[a].adj) {
        int b = i.second;
        if(!v[b].vis){
            cyc = max(cyc, precDfs(b, a));
        }
        else if(v[b].vis && b != p){
            cyc = b;
        }
    }
    if(cyc != -1){
        v[a].isCyc = 1;
        cycles.back().push_back(a);
    }
    if(cyc == a) return -1;
    return cyc;
}

int ddfs(int a){
    v[a].vis = 2;
    int mxd = 0;
    for (auto &i : v[a].adj) {
        node b = v[i.second];
        if(b.vis < 2 && !b.isCyc){
            mxd = max(mxd, ddfs(i.second) + i.first);
        }
    }
    v[a].mxd = mxd;
    return mxd;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n; cin >> n;
    v.resize(n);
    for (int i = 0; i < n; i++) {    
        int a, l; cin >> a >> l; a--;
        v[i].binDp.push_back(l);
        v[i].binSum.push_back(l);
        v[i].binJmp.push_back(a);
        v[i].adj.push_back({l, a});
        v[a].adj.push_back({l, i});
    }
    for (int i = 0; i < n; i++) sort(all(v[i].adj), greater<pair<int, int>>());

    for (int i = 0; i < n; i++) {
        v[i].binJmp.resize(20);
        v[i].binSum.resize(20);
        v[i].binDp.resize(20);
        if(!v[i].vis){
            cycles.push_back({});
            precDfs(i, i);
        }
    }

    for (int i = 0; i < n; i++) {
        if(v[i].vis < 2 && v[i].isCyc){
            ddfs(i);
        }
    }
    
    int res = 0;
    for (int i = 0; i < cycles.size(); i++) {
        for (int j = 0; j < cycles[i].size(); j++) {
            int a = cycles[i][j];
            v[a].binDp[0] += v[v[a].binJmp[0]].mxd;
        }
        for (int k = 1; k < 20; k++) {
            for (int j = 0; j < cycles[i].size(); j++) {
                int a = cycles[i][j];
                int b = v[a].binJmp[k - 1];
                v[a].binSum[k] = v[a].binSum[k - 1] + v[b].binSum[k - 1];
                v[a].binJmp[k] = v[b].binJmp[k - 1];
                int x = v[a].binDp[k - 1];
                int y = v[a].binSum[k - 1] + v[b].binDp[k - 1];
                v[a].binDp[k] = max(x, y);
            }
        }
        int cmx = 0;
        int mxJmp = cycles[i].size() - 1;
        for (int k = 0; k < cycles[i].size(); k++) {
            int dp = 0;
            int cur = cycles[i][k];
            int s = 0;
            for (int j = 19; j >= 0; j--) {
                if(mxJmp & (1 << j)){
                    dp = max(dp, s + v[cur].binDp[j]);
                    cur = v[cur].binJmp[j];
                    s += v[cur].binSum[j];
                }
            }
            cmx = max(cmx, dp + v[cycles[i][k]].mxd);
        }
        res += cmx;
    }
    cout << res << endl;
}

Compilation message (stderr)

islands.cpp: In function 'int main()':
islands.cpp:86:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   86 |     for (int i = 0; i < cycles.size(); i++) {
      |                     ~~^~~~~~~~~~~~~~~
islands.cpp:87:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   87 |         for (int j = 0; j < cycles[i].size(); j++) {
      |                         ~~^~~~~~~~~~~~~~~~~~
islands.cpp:92:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   92 |             for (int j = 0; j < cycles[i].size(); j++) {
      |                             ~~^~~~~~~~~~~~~~~~~~
islands.cpp:104:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  104 |         for (int k = 0; k < cycles[i].size(); k++) {
      |                         ~~^~~~~~~~~~~~~~~~~~

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