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Submission #986959

# Submission time Handle Problem Language Result Execution time Memory
986959 2024-05-21T16:00:48 Z AverageAmogusEnjoyer One-Way Streets (CEOI17_oneway) C++17
60 / 100
 3000 ms 17712 KB 
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
 
template<class T> bool cmin(T &i,T j) { return i > j ? i = j,true: false; }
template<class T> bool cmax(T &i,T j) { return i < j ? i = j,true: false; }

struct RMQ {
    int n;
    int lg;
    vector<vector<int>> sparse;
    RMQ() {}
    RMQ(vector<int> a) {
        if (a.empty()) { return; }
        n = (int)a.size();
        lg = 0;
        while((1<<lg) <= n) { lg++; }
        sparse.assign(lg,vector<int>(n));
        sparse[0] = a;
        for (int pw=1;pw<lg;pw++) {
            for (int i=0;i<n;i++) {
                sparse[pw][i] = min(sparse[pw-1][i],sparse[pw-1][min(i+(1<<(pw-1)),n-1)]);
            }
        }
    }
    int qry(int l,int r) {
        assert(0 <= l && l <= r && r < n);
        int bit = 31-__builtin_clz(r-l+1);
        return min(sparse[bit][l],sparse[bit][r-(1<<bit)+1]);
    }
};

struct LCA {
    int n;
    vector<vector<pair<int,int>>> adj;
    vector<int> tin,path,ret;
    RMQ rmq;
    int timer = 0;
    LCA(int N,vector<vector<pair<int,int>>> a) {
        adj = a;
        n = N;
        tin.resize(n);
        dfs();
        rmq = RMQ(ret);       
    }
    void dfs(int x=0,int z=-1) {
        tin[x] = timer++;
        for (auto &[y,idx]: adj[x]) if (y != z) {
            path.push_back(x),ret.push_back(tin[x]);
            dfs(y,x);
        }
    }
    int lca(int x,int y) { 
        if (x == y) { return x; }
        if (tin[x] > tin[y]) { swap(x,y); }
        return path[rmq.qry(tin[x],tin[y]-1)];
    }
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, m;
    cin >> n >> m;
    string ans(m,'B');
    vector<vector<pair<int,int>>> adj(n);
    vector<pair<int,int>> edges(m);
    for (int i=0,x,y;i<m;i++) {
        cin >> x >> y;
        --x,--y;
        edges[i] = make_pair(x,y);
        adj[x].emplace_back(y,i);
        adj[y].emplace_back(x,i);
    }
    vector<vector<pair<int,int>>> tree(n);
    // vector<vector<pair<int,int>>> back_edges(n);
    vector<int> dp(n);
    vector<int> t(n,-1);
    int timer = 0;
    vector<bool> vst(n);
    vector<int> par(n);
    auto dfs = [&](auto &self,int x,int z) -> void {
        t[x] = timer++;
        vst[x]=true;
        par[x]=z;
        for (auto &[y,idx]: adj[x]) if (y != z) {
            if (t[y] > t[x]) {
                // back_edges[y].emplace_back(x,idx);
                // cout << "back edge: " << y+1 << " " << x+1 << endl;
                dp[y]++;
                dp[x]--;
            } else if (t[y] == -1) {
                tree[x].emplace_back(y,idx);
                // cout << "span edge: " << x+1 << " " << y+1 << endl;
                self(self,y,x);
            }
        }
    };
    vst.assign(n,false);
    for (int x=0;x<n;x++) if (!vst[x]) { 
        dfs(dfs,x,-1);
    }
    auto dfstree = [&](auto &self,int x,int z) -> void {
        vst[x]=true;
        for (auto &[y,idx]: tree[x]) if (y != z) {
            self(self,y,x);
            dp[x] += dp[y];
        }
    };
    vst.assign(n,false);
    for (int x=0;x<n;x++) if (!vst[x]) { 
        dfstree(dfstree,x,-1);
    }
    vector<int> up(n),down(n);
    // LCA tr(n,tree);
    int q;
    cin >> q;
    for (int x,y;q--;) {
        cin >> x >> y;
        --x,--y;
        // int l = tr.lca(x,y);
        vst.assign(n,false);
        int cx = x;
        while(cx != -1) {
            vst[cx] = true;
            cx = par[cx];
        }
        int cy = y;
        while(!vst[cy]) {
            cy = par[cy];
            assert(cy != -1);
        }
        int l = cy;
        up[x]++;
        up[l]--;
        down[y]++;
        down[l]--;
    }
    auto dfspush = [&](auto &self,int x,int z) -> void {
        vst[x]=true;
        for (auto &[y,idx]: tree[x]) if (y != z) {
            self(self,y,x);
            up[x] += up[y];
            down[x] += down[y];
        
            // actually write down edge
            if (dp[y] != 0) { continue; } 
            assert(up[y] == 0 || down[y] == 0);
            if (up[y]) {
                if (edges[idx].second == x) {
                    ans[idx] = 'R';
                } else {
                    ans[idx] = 'L';
                }
            } else if (down[y]) {
                if (edges[idx].second == y) {
                    ans[idx] = 'R';
                } else {
                    ans[idx] = 'L';
                }
            }
        }
    };
    vst.assign(n,false);
    for (int x=0;x<n;x++) if (!vst[x]) { 
        dfspush(dfspush,x,-1); 
    }
    cout << ans << endl;    
}

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 344 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 388 KB Output is correct
5 Correct 1 ms 604 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 600 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 348 KB Output is correct
10 Correct 1 ms 348 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 344 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 388 KB Output is correct
5 Correct 1 ms 604 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 600 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 348 KB Output is correct
10 Correct 1 ms 348 KB Output is correct
11 Correct 32 ms 7712 KB Output is correct
12 Correct 45 ms 9688 KB Output is correct
13 Correct 45 ms 12112 KB Output is correct
14 Correct 55 ms 14928 KB Output is correct
15 Correct 75 ms 15816 KB Output is correct
16 Correct 42 ms 14672 KB Output is correct
17 Correct 60 ms 16644 KB Output is correct
18 Correct 43 ms 14680 KB Output is correct
19 Correct 61 ms 17712 KB Output is correct
20 Correct 39 ms 11088 KB Output is correct
21 Correct 37 ms 10576 KB Output is correct

Subtask #3
0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 344 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 1 ms 388 KB Output is correct
5 Correct 1 ms 604 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 1 ms 600 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 1 ms 348 KB Output is correct
10 Correct 1 ms 348 KB Output is correct
11 Correct 32 ms 7712 KB Output is correct
12 Correct 45 ms 9688 KB Output is correct
13 Correct 45 ms 12112 KB Output is correct
14 Correct 55 ms 14928 KB Output is correct
15 Correct 75 ms 15816 KB Output is correct
16 Correct 42 ms 14672 KB Output is correct
17 Correct 60 ms 16644 KB Output is correct
18 Correct 43 ms 14680 KB Output is correct
19 Correct 61 ms 17712 KB Output is correct
20 Correct 39 ms 11088 KB Output is correct
21 Correct 37 ms 10576 KB Output is correct
22 Execution timed out 3021 ms 17000 KB Time limit exceeded
23 Halted 0 ms 0 KB -