Submission #581675

#	Time	Username	Problem	Language	Result	Execution time	Memory
581675		elpro123	Graph (BOI20_graph)	C++14	100 / 100	315 ms	27184 KiB

Graph

#include <bits/stdc++.h>

using namespace std;
 
/*
- Los valores de los distintos componentes conectados son independientes entre sí.
- Cuando se hace un DFS de un CC(componente conectado), el vértice inicial tiene un valor de x
- Para cada eje (a, b, c)
    Si b no está explorado, valor[b] = c - valor[a]
    Si b está explorado, pero la expresion c = valor[a] + valor[b] no da 
    ninguna información adicional, no se hace nada
    Si b está explorado, y la expresión da información adicional, se usa para calcular x.
    para evitar WA verificar el resultado
*/
 

vector<int> eje[100001];
vector<int> color[100001];
vector<double> coefx(100001, 0.0);
vector<double> coefc(100001, 0.0);
vector<int> componentes(100001, 0);
vector<double> xval(1);
vector<double> findx;
int comp_cnt = 0;
 
void dfs(int u){
    findx.push_back(coefc[u] * coefx[u] * -1.0);
    for(int i = 0; i < eje[u].size(); i++){
        int v = eje[u][i];
        int c = color[u][i];
 
        if(!componentes[v]){
            componentes[v] = comp_cnt;
            coefx[v] = -1.0 * coefx[u];
            coefc[v] = double(c) - coefc[u];
            dfs(v);
        }else{
            if(coefx[u] + coefx[v] == 0.0) continue;
            xval.back() = (double(c) - (coefc[u] + coefc[v]))/(coefx[u] + coefx[v]);
        }
    }
}
 
int main(){
    int n, m;
    cin>>n>>m;
 
    int a, b, c;
    for(int i = 1; i <= m; i++){
        cin>>a>>b>>c;
 
        eje[a].push_back(b);
        color[a].push_back(c);
 
        eje[b].push_back(a);
        color[b].push_back(c);
    }
 
    for(int i = 1; i <= n; i++){
        if(componentes[i]) continue;
        comp_cnt++;
        componentes[i] = comp_cnt;
        coefx[i] = 1.0;
        xval.push_back(-9999.9);
        findx.clear();
        dfs(i);
        if(xval.back() == -9999.9){
            sort(findx.begin(), findx.end());
            xval.back() = findx[findx.size()/2];
        }
    }
 
    double val[n+1];
    for(int i = 1; i <= n; i++){ 
        val[i] = coefx[i] * xval[componentes[i]] + coefc[i];
    }
    for(int i = 1; i <= n; i++){
        for(int j = 0; j < eje[i].size(); j++){
            if(val[i] + val[eje[i][j]] != color[i][j]){
                cout<<"NO\n";
                return 0;
            }
        }
    }
    cout<<"YES\n";
    for(int i = 1; i <= n; i++){
        cout << val[i] << ' ';
    }
    cout << '\n';
}

Compilation message (stderr)

Graph.cpp: In function 'void dfs(int)':
Graph.cpp:28:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 |     for(int i = 0; i < eje[u].size(); i++){
      |                    ~~^~~~~~~~~~~~~~~
Graph.cpp: In function 'int main()':
Graph.cpp:78:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |         for(int j = 0; j < eje[i].size(); j++){
      |                        ~~^~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 17 / 17
• Subtask 4: 24 / 24
• Subtask 5: 42 / 42