Hook!!!

Hello everyone!

If you are struggling with graph problems, this post will save you a LOT of time. Today I will explain one of the most powerful techniques — DFS (Depth-First Search)

What is DFS? DFS is a technique where we go as deep as possible in a graph before backtracking.

In simple words: Go forward → go deeper → if stuck → go back

Where is it used? DFS is used in:

1) Connected components 2) Cycle detection 3) Tree traversal 4) Grid problems (VERY COMMON)

Pattern If you see:

• "graph"
• "visit all nodes"
• "connected"
• "grid"

Think about DFS immediately

Code (C++) **#include <bits/stdc++.h> using namespace std;

const int N = 200005;

vector g[N]; bool vis[N];

void dfs(int v) { vis[v] = true;

for (int to : g[v]) {
    if (!vis[to]) {
        dfs(to);
    }
}

}

int main() { int n, m; cin >> n >> m;

for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    g[u].push_back(v);
    g[v].push_back(u);
}

int cnt = 0;

for (int i = 1; i <= n; i++) {
    if (!vis[i]) {
        dfs(i);
        cnt++;
    }
}

cout << cnt << "\n";

}**

Final Tip DFS is one of the easiest ways to gain rating on Codeforces.

Master it → solve 50+ problems → you will feel huge progress

Ending Thanks for reading!

If this post helped you: please upvote Good Bye!