谁能告诉我,当我使用 for 循环获取存储在级别“it”中的节点数时,为什么它不起作用?
请告诉我其他方法可以访问具有基于范围的 for 循环的 vector 。
// A simple representation of graph using STL
#include<iostream>
#include<vector>
using namespace std;
// A utility function to add an edge in an
// undirected graph.
void addEdge(vector<int> adj[], int u, int v)
{
adj[u].push_back(v);
adj[v].push_back(u);
}
void printNodes(vector<int> adj[], int n)
{ int count=0;
for (auto x : adj[n]){
count++;
}
cout<<count;
}
// Driver code
int main()
{
int V,x,y;
cin>>V;
vector<int> adj[V+1];
for(int i=0;i<V-1;i++){
cin>>x>>y;
addEdge(adj, x, y);
}
int it;
cin>>it;
printNodes(adj, it);
return 0;
}
最佳答案
首先,您的方法中缺少一些东西:
所以这是最终的代码:
#include<iostream>
#include<vector>
#include<queue>
using namespace std;
int nodes_at_level[10];
// Taken from hackerearth.....
int level[10]; //To determine the level of each node
bool vis[10]; //Mark the node if visited
void bfs(int s,vector<int> adj[]) {
queue <int> q;
q.push(s);
level[ s ] = 0 ; //Setting the level of the source node as 0
nodes_at_level[level[s]]++;
vis[ s ] = true;
while(!q.empty())
{
int p = q.front();
q.pop();
for(int i = 0;i < adj[ p ].size() ; i++)
{
if(vis[ adj[ p ][ i ] ] == false)
{
//Setting the level of each node with an increment in the level of parent node
level[ adj[ p ][ i ] ] = level[ p ]+1;
nodes_at_level[level[ adj[ p ][ i ] ]]++;
q.push(adj[ p ][ i ]);
vis[ adj[ p ][ i ] ] = true;
}
}
}
}
void addEdge(vector<int> adj[], int u, int v)
{
adj[u].push_back(v);
adj[v].push_back(u);
}
//to print the number of nodes in the level 'it'
void printNodes(vector<int> adj[], int n)
{
int count = 0;
count = nodes_at_level[n];
cout << count;
}
// Driver code
int main()
{
int V, x, y ,E;
cin >> E;
cin >> V;
vector<int> adj[V+1];
for (int i = 0; i < E; i++) {
cin >> x >> y;
addEdge(adj, x, y);
}
bfs(1,adj); //assuming the start of the graph to be 1
int it;
cin >> it;
printNodes(adj, it);
return 0;
}
我已经看过hackerearth问题了。但只是试图解决你的问题。
但是,如果您无论如何都想要for循环,那么试试这个...我只是根据顶点的级别存储顶点..
vector<int> nodes_at_level[10];
//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// Taken from hackerearth.....
int level[10]; //To determine the level of each node
bool vis[10]; //Mark the node if visited
void bfs(int s,vector<int> adj[]) {
queue <int> q;
q.push(s);
level[ s ] = 0 ; //Setting the level of the source node as 0
nodes_at_level[level[s]].push_back(s);
vis[ s ] = true;
while(!q.empty())
{
int p = q.front();
q.pop();
for(int i = 0;i < adj[ p ].size() ; i++)
{
if(vis[ adj[ p ][ i ] ] == false)
{
//Setting the level of each node with an increment in the level of parent node
level[ adj[ p ][ i ] ] = level[ p ]+1;
nodes_at_level[level[ adj[ p ][ i ] ]].push_back(adj[p][i]);
//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
q.push(adj[ p ][ i ]);
vis[ adj[ p ][ i ] ] = true;
}
}
}
}
//to print the number of nodes in the level 'it'
void printNodes(vector<int> adj[], int n)
{
int count=0;
for (auto x : nodes_at_level[n]){
count++;
}
cout<<count;
}
希望它可能会有所帮助。
关于c++ - 为什么我的 for 循环给出错误 : X does not name a type,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/61982046/