Added content for CP class 7

CompetitiveProgramming/2021_10_31_CPClass-7/Codes/bfs.cpp

@@ -0,0 +1,82 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// adjacency list of unweighted graph
+vector<vector<int>> a;
+
+// adjacency list of weighted graph
+vector<vector<pair<int, int>>> adj;
+
+vector<bool> used;
+vector<int> d , p;
+
+// BFS for any graph
+void bfs(int s) {   // s -> root
+    queue<int> q;
+    q.push(s);
+    used[s] = true;
+    p[s] = -1;
+    while (!q.empty()) {
+        int v = q.front();
+        q.pop();
+        for (int u : a[v]) {
+            if (!used[u]) {
+                used[u] = true;
+                q.push(u);
+                d[u] = d[v] + 1;
+                p[u] = v;
+            }
+            else {
+                if(u = p[v]) {
+                    continue;
+                }
+                // graph has cycle
+                return;
+            }
+        }
+    }
+}
+
+void bfs01(int s) {   // s -> root
+    deque<int> q;
+    q.push_back(s);
+    used[s] = true;
+    while (!q.empty()) {
+        int v = q.front();
+        q.pop_front();
+        for (pair<int , int> p : adj[v]) {
+            int u = p.first;
+            int w = p.second;
+            if (!used[u]) {
+                if(w == 0) {
+                    d[u] = d[v];
+                    q.push_front(u);
+                    used[u] = true;
+                }
+                else {
+                    used[u] = true;
+                    q.push_back(u);
+                    d[u] = d[v] + 1;
+                }
+            }
+        }
+    }
+}
+
+int main() {
+    int n , m;
+    cin >> n >> m;
+    used.resize(n);
+    a.resize(n);
+    p.resize(n);
+    d.resize(n);
+    adj.resize(n);
+    for(int i = 0 ; i < m ; i++) {
+        int x , y , w;
+        cin >> x >> y >> w;
+        a[x].push_back(y);
+        adj[x].push_back({y , w});
+    }
+
+    bfs(0);
+}

CompetitiveProgramming/2021_10_31_CPClass-7/Codes/dfs.cpp

@@ -0,0 +1,54 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// adjacency list of unweighted graph
+vector<vector<int>> a;
+
+// adjacency list of weighted graph
+vector<vector<pair<int, int>>> adj;
+
+vector<int> visited;
+
+// DFS for any graph
+void dfs(int s) {
+    visited[s] = 1;
+    for(int i = 0 ; i < a[s].size() ; i++) {
+        if(!visited[a[s][i]]) {
+            dfs(a[s][i]);
+        }
+    }
+}
+
+/*
+    dfs(1) -> dfs(2) -> dfs(3) -> dfs(2) -> dfs(4) -> dfs(2) -> dfs(1) -> dfs(5) -> dfs(6) -> dfs(5) -> dfs(1) -> main
+*/
+
+
+// Tree DFS. We only to need to make sure that we don't go back to the parent.
+void tree_dfs(int s , int p = -1) {
+    for(int i = 0 ; i < a[s].size() ; i++) {
+        if(a[s][i] != p) {
+            tree_dfs(a[s][i] , s);
+        }
+    }
+}
+
+int main() {
+    int n , m;
+    cin >> n >> m;
+    visited.resize(n);
+    a.resize(n);
+    adj.resize(n);
+    for(int i = 0 ; i < m ; i++) {
+        int x , y , w;
+        cin >> x >> y >> w;
+        a[x].push_back(y);
+        adj[x].push_back({y , w});
+    }
+
+    for(int i = 0 ; i < n ; i++) {
+        if(!visited[i])
+            dfs(i);
+    }
+    tree_dfs(0);
+}

CompetitiveProgramming/2021_10_31_CPClass-7/README.md

@@ -0,0 +1,19 @@
+# Competitive Programming Class 7
+
+## Get the presentation used in class: [Here](./Graph_Traversals.pdf) 
+
+## Get the class recording: [Here](https://drive.google.com/file/d/1p1VladoCu1PHSA6hGY0KMjU0xQiGKP73/view?usp=sharing)
+
+#### October 31, 2021
+
+<hr>
+
+## Class Coverage
+
+- Graph Traversals (Implementation Details and problems)
+
+## Additional Resources
+
+- [Graph Algorithms](https://codeforces.com/blog/entry/16221)
+- [DFS Tutorial](https://www.hackerearth.com/practice/algorithms/graphs/depth-first-search/tutorial/)
+- [Bipartite Check](https://cp-algorithms.com/graph/bipartite-check.html)

CompetitiveProgramming/README.md

@@ -9,6 +9,7 @@
 -   [Class 4 (Problems on Dynamic Programming): held on August 15, 2021](2021_08_15_CPClass-4)
 -   [Class 5 (DP tricks and Bitmask DP): held on August 21, 2021](2021_08_21_CPClass-5)
 -   [Class 6 (SOS DP and Intro to Graphs): held on October 27, 2021](2021_10_27_CPClass-6)
+-   [Class 7 (Graph Traversals Implementation Details): held on October 31, 2021](2021_10_31_CPClass-7)
 
 ## Reading Resources
 

README.md

@@ -53,6 +53,7 @@ If you are a part of MNNIT join us on Microsoft Team [MNNIT CC Queries Official]
     - [Competitive Programming Class-4](CompetitiveProgramming/2021_08_15_CPClass-4)
     - [Competitive Programming Class-5](CompetitiveProgramming/2021_08_21_CPClass-5)
     - [Competitive Programming Class-6](CompetitiveProgramming/2021_10_27_CPClass-6)
+    - [Competitive Programming Class-7](CompetitiveProgramming/2021_10_31_CPClass-7)
 
 - [Git/GitHub classes](Git-GitHub)
     - [Git Class-1](Git-GitHub/2021_04_20_GitClass-1)