#include <iostream>
using namespace std;
int tmp[1000001];
int arr[100001];
int main(void)
{
ios::sync_with_stdio(0);
cin.tie(NULL); cout.tie(NULL);
int n, x;
int count = 0;
cin >> n;
for (int i = 0; i < n; i++)
cin >> arr[i];
cin >> x;
for (int i = 0; i < n; i++) {
if (tmp[x - arr[i]] == 1) count++;
else tmp[arr[i]] = 1;
}
cout << count;
return 0;
}
DFS가 헷갈려서 시작 단계 예제 코드로 공부해보기 - 출처 Geeks for Geeks
1.
// C++ program to print DFS traversal from
// a given vertex in a given graph
#include <bits/stdc++.h>
using namespace std;
// Graph class represents a directed graph
// using adjacency list representation
class Graph
{
public:
map<int, bool> visited;
map<int, list<int>> adj;
// function to add an edge to graph
void addEdge(int v, int w);
// DFS traversal of the vertices
// reachable from v
void DFS(int v);
};
void Graph::addEdge(int v, int w)
{
adj[v].push_back(w); // Add w to v’s list.
}
void Graph::DFS(int v)
{
// Mark the current node as visited and
// print it
visited[v] = true;
cout << v << " ";
// Recur for all the vertices adjacent
// to this vertex
list<int>::iterator i;
for (i = adj[v].begin(); i != adj[v].end(); ++i)
if (!visited[*i])
DFS(*i);
}
// Driver code
int main()
{
// Create a graph given in the above diagram
Graph g;
g.addEdge(0, 1);
g.addEdge(0, 2);
g.addEdge(1, 2);
g.addEdge(2, 0);
g.addEdge(2, 3);
g.addEdge(3, 3);
cout << "Following is Depth First Traversal"
" (starting from vertex 2) \n";
g.DFS(2);
return 0;
}
Output
Following is Depth First Traversal (starting from vertex 2) 2 0 1 3
// C++ program to print DFS
// traversal for a given given
// graph
#include <bits/stdc++.h>
using namespace std;
class Graph {
// A function used by DFS
void DFSUtil(int v);
public:
map<int, bool> visited;
map<int, list<int>> adj;
// function to add an edge to graph
void addEdge(int v, int w);
// prints DFS traversal of the complete graph
void DFS();
};
void Graph::addEdge(int v, int w)
{
adj[v].push_back(w); // Add w to v’s list.
}
void Graph::DFSUtil(int v)
{
// Mark the current node as visited and print it
visited[v] = true;
cout << v << " ";
// Recur for all the vertices adjacent to this vertex
list<int>::iterator i;
for (i = adj[v].begin(); i != adj[v].end(); ++i)
if (!visited[*i])
DFSUtil(*i);
}
// The function to do DFS traversal. It uses recursive
// DFSUtil()
void Graph::DFS()
{
// Call the recursive helper function to print DFS
// traversal starting from all vertices one by one
for (auto i:adj)
if (visited[i.first] == false)
DFSUtil(i.first);
}
// Driver Code
int main()
{
// Create a graph given in the above diagram
Graph g;
g.addEdge(0, 1);
g.addEdge(0, 9);
g.addEdge(1, 2);
g.addEdge(2, 0);
g.addEdge(2, 3);
g.addEdge(9, 3);
cout << "Following is Depth First Traversal \n";
g.DFS();
return 0;
}
Output
Following is Depth First Traversal 0 1 2 3 9
#include <algorithm>
#include <iostream>
using namespace std;
double arr[1001];
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int N;
cin >> N;
for (int i=0; i<N; i++) {
cin >> arr[i];
}
sort(arr, arr+N, greater<int>());
double M = arr[0];
double sum = 0;
if (M==0) cout << 0;
else {
for (int j=0; j<N; j++) {
arr[j] = arr[j]/M*100;
sum = sum+arr[j];
}
cout << sum/double(N);
}
return 0;
}
다른 분의 풀이를 참고했는데, 효율적으로 쓰기 위해 아스키코드를 이용해 문자를 바로 숫자배열로 매핑하는 방식을 쓴다
include <iostream>
#include <cstring>
#include <algorithm>
#include <string>
using namespace std;
int main() {
int arr[26] = { 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 10, 10, 10, 10 };
int sum = 0;
string input
cin >> input;
for (int i = 0; i < input.length(); i++) {
int index = input[i] - 65;
sum += arr[index];
}
cout << sum << '\n';
return 0;
}
Deque 를 디큐라고 불렀었는데 덱이라고 뷰르는건지 처음 알았다😅
#include <iostream>
#include <deque>
using namespace std;
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int N, X;
deque<int> D;
string op;
cin >> N;
for (int i = 0; i < N; i++) {
cin >> op;
if (op == "push_front") {
cin >> X;
D.push_front(X);
}
else if (op == "push_back") {
cin >> X;
D.push_back(X);
}
else if (op == "pop_front") {
if (D.empty()) cout << -1 << '\n';
else {
cout << D.front() << '\n';
D.pop_front();
}
}
else if (op == "pop_back") {
if (D.empty()) cout << -1 << '\n';
else {
cout << D.back() << '\n';
D.pop_back();
}
}
else if (op == "size") {
cout << D.size() << '\n';
}
else if (op == "empty") {
cout << D.empty() << '\n';
}
else if (op == "front") {
if (D.empty()) cout << -1 << '\n';
else cout << D.front() << '\n';
}
else if (op == "back") {
if (D.empty()) cout << -1 << '\n';
else cout << D.back() << '\n';
}
}
return 0;
}