Patch 1

Graph/DFS.cpp

@@ -0,0 +1,27 @@
+#include<bits/stdc++.h>
+#define pb push_back
+using namespace std;
+const int LIM = 50;
+int vis[LIM];
+vector<vector<int> >AdjList(LIM);
+void dfs(int u){
+	cout<<u<<" , ";
+	vis[u]=1;
+	for(auto v:AdjList[u]){
+		if(vis[v]==0){
+			dfs(v);
+		}
+	}
+}
+int main(){
+	int n,m;
+	cin>>n>>m;
+	for(int i=0;i<m;i++){
+		int u,v;
+		cin>>u>>v;
+		AdjList[u].pb(v);
+		AdjList[v].pb(u);
+	}
+	dfs(1);
+
+}

Maths/EulerGCD.cpp

@@ -0,0 +1,18 @@
+#include<bits/stdc++.h>
+using namespace std;
+int iterativeGcd(int a,int b){
+	while(a!=0){
+		int rem = b%a;
+		b = a;
+		a = rem;
+	}
+	return b;
+}
+int recursiveGcd(int a, int b){
+	if(a==0)return b;
+	return recursiveGcd(b%a,a);
+}
+int main(){
+	int a = 6,b=4;
+	cout<<recursiveGcd(a,b);
+}

Maths/FastExponentiation.cpp

@@ -0,0 +1,30 @@
+#include<bits/stdc++.h>
+#define ll long long
+using namespace std;
+ll fastExpo(ll base, ll power){
+	if(power==0)
+		return 1;
+	ll temp = fastExpo(base,power/2);
+	if(power&1){
+		return temp*temp * base;
+	}
+	return temp*temp;
+}
+ll fastExpoIterative(ll base, ll power){
+	ll res = 1;
+	while(power	>0){
+		if(power&1){
+			res*=base;
+		}
+		power/=2;
+		base*=base;
+	}
+	return res;
+
+}
+int main(){	
+	ll base = 5;
+	ll power = 3;
+	cout<<fastExpoIterative(base,power);
+
+}

README.md

@@ -1,2 +1,8 @@
-# Competitive-Programming-Algos
-C++ implementation of algorithms learned and used while competitive programming
+# Competitive Programming Runbook
+During the years I spent playing around with competetive programming, here's an archive I prepared for the most useful reusable content I have been through.
+I'm in the phase of collecting all my codes, making them generic enough to be understood/reused, and put it here.
+Feel free to contribute, but make sure to maintain the quality - 
+<ul>
+<li>Don't add a problem's solution here, as that's not reusable.</li>
+<li>Let's have generic snippets one can refer for learning algo/implementation</li>
+</ul>

Searching/BinarySearch.cpp

@@ -0,0 +1,36 @@
+#include<bits/stdc++.h>
+using namespace std;
+//Create a predicate to return T/F for an ind
+bool predicate(vector<int>&v, int ind, int search_token){
+	return v[ind] >= search_token;
+}
+int binarySeach(vector<int>&v, int search_token){
+	int low = 0,high = v.size(),mid;
+	while(low<high){
+		mid = (low+high)/2;
+		if(predicate(v,mid,search_token)){
+			high = mid;
+		}
+		else
+			low = mid+1;
+	}
+	if(v[low]==search_token) return low;
+	return -1;
+}
+int recursiveBinarySearch(vector<int>&v, int search_token, int begin, int end){
+	if(begin==end){
+		if(v[begin]==search_token)
+			return begin;
+		return -1;
+	}
+	int mid = (begin+end)/2;
+	if(predicate(v,mid,search_token)){
+		return recursiveBinarySearch(v,search_token,begin,mid);
+	}
+	return recursiveBinarySearch(v,search_token,mid+1,end);
+}
+int main(){
+	vector<int> v = {1,2,4,5,11,20,25};
+	cout<<recursiveBinarySearch(v,6,0,6);
+	return 0;
+}

Sorting/BubbleSort.java

@@ -0,0 +1,34 @@
+public class BubbleSortExample {  
+    static void bubbleSort(int[] arr) {  
+        int n = arr.length;  
+        int temp = 0;  
+        for(int i=0; i < n; i++){  
+            for(int j=1; j < (n-i); j++){  
+                if(arr[j-1] > arr[j]){  
+                         //swap elements  
+                         temp = arr[j-1];  
+                         arr[j-1] = arr[j];  
+                         arr[j] = temp;  
+                }  
+
+             }  
+         }
+    }  
+    public static void main(String[] args) {  
+        int arr[] ={3,60,35,2,45,320,5};  
+
+        System.out.println("Array Before Bubble Sort");  
+        for(int i=0; i < arr.length; i++){  
+                System.out.print(arr[i] + " ");  
+        }  
+        System.out.println();  
+
+        bubbleSort(arr);//sorting array elements using bubble sort  
+
+        System.out.println("Array After Bubble Sort");  
+        for(int i=0; i < arr.length; i++){  
+                System.out.print(arr[i] + " ");  
+        }  
+
+    }  
+}  

Sorting/HeapSort.cpp

@@ -0,0 +1,40 @@
+#include<bits/stdc++.h>
+#define sz(v) ((int)v.size())
+using namespace std;
+void heapify(vector<int>&v, int SIZE, int ind){
+	int left_child = (ind<<1)+1;
+	int right_child = left_child+1;
+	int to_swap;
+	if(left_child<SIZE && v[left_child] > v[ind])
+		to_swap = left_child;
+	else
+		to_swap = ind;
+	if(right_child<SIZE && v[right_child] > v[to_swap])
+		to_swap = right_child;
+	if(to_swap !=ind){
+		int temp = v[to_swap];
+		v[to_swap] = v[ind];
+		v[ind] = temp;
+		heapify(v,SIZE,to_swap);
+	}
+}
+void heapSort(vector<int>&v){
+	vector<int>heap(sz(v));
+	for(int i=(sz(v)-2)/2;i>=0;i--){
+		heapify(v,sz(v),i);
+	}
+	for(int i=sz(v)-1;i>0;i--){
+		int temp = v[0];
+		v[0] = v[i];
+		v[i] = temp;
+
+		heapify(v,i,0);
+	}
+}
+int main(){
+	vector<int>temp = {1,3,2,12,444,5};
+	heapSort(temp);
+	for(int v:temp){
+		cout<<v<<" ";
+	}
+}

Sorting/LinearSort.cpp

@@ -0,0 +1,21 @@
+#include<bits/stdc++.h>
+using namespace std;
+void linearSort(vector<int>&v){
+	for(int i=0;i<v.size();i++){
+		for(int j=i+1;j<v.size();j++){
+			if(v[j]<v[i]){
+				int temp = v[i];
+				v[i] = v[j];
+				v[j] = temp;
+			}
+		}
+
+	}
+}
+int main(){
+	vector<int>temp = {1,3,2,12,444,5};
+	linearSort(temp);
+	for(int v:temp){
+		cout<<v<<" ";
+	}
+}

Sorting/MergeSort.cpp

@@ -0,0 +1,33 @@
+#include<bits/stdc++.h>
+using namespace std;
+void merge(vector<int>&v, int startIndex, int mid, int endIndex){
+	vector<int>temp;
+	int i1 = startIndex;
+	int i2 = mid+1;
+	while(i1<=mid && i2<=endIndex){
+		if(v[i1]<=v[i2])
+			temp.push_back(v[i1]),i1++;
+		else
+			temp.push_back(v[i2]),i2++;
+	}
+	while(i1<=mid)temp.push_back(v[i1]),i1++;
+	while(i2<=endIndex)temp.push_back(v[i2]),i2++;
+	for(int i=0;i<temp.size();i++)
+		v[startIndex+i] = temp[i];
+}
+void mergeSort(vector<int>&v, int startIndex, int endIndex){
+	if(startIndex<endIndex){
+		int mid = (startIndex+endIndex)/2;
+		mergeSort(v,startIndex,mid);
+		mergeSort(v,mid+1,endIndex);
+		merge(v,startIndex,mid,endIndex);	
+	}
+
+}
+int main(){
+	vector<int>temp = {1,3,2,12,444,5};
+	mergeSort(temp,0, temp.size()-1);
+	for(int v:temp){
+		cout<<v<<" ";
+	}
+}

StringSearching/Kmp.cpp

@@ -0,0 +1,36 @@
+#include<bits/stdc++.h>
+using namespace std;
+void kmpPreProcess(string pattern, vector<int>&lps){
+	int i = 0,j=-1;
+	lps[0] = -1;
+	while(i<pattern.size()){
+		while(j>=0 && pattern[i]!=pattern[j])j = lps[j];
+		i++,j++;
+		lps[i]=j;
+	}
+}
+vector<int> kmpSearch(string text, string pattern){
+	vector<int> ans;
+	vector<int> lps(pattern.size()+1);
+	kmpPreProcess(pattern, lps);
+	int i = 0, j=-1;
+	while(i<text.size()){
+		while(j>=0 && pattern[j]!=text[i])j=lps[j];
+		i++;j++;
+		if(j==pattern.size()){
+			ans.push_back(i-pattern.size());
+			j = lps[j];
+		}
+	}
+	return ans;
+}
+int main(){
+
+	string text = "Hey there! this is a text string, within which we wanna search a pattern.  \
+	Note that pattern repeats itself, so search for pattern if you wanna see can this report multiple occurrences of pattern.";
+	string pattern = "pattern";
+	vector<int> indices = kmpSearch(text,pattern);
+	for(auto i:indices){
+		cout<<i<<",";
+	}
+}

StringSearching/LinearSearch.cpp

@@ -0,0 +1,27 @@
+#include<bits/stdc++.h>
+using namespace std;
+vector<int> linearSearch(string text, string pattern){
+	vector<int>ans;
+	for(int i=0;i<text.size();i++){
+		bool found = true;
+		for(int j=0;j<pattern.size();j++){
+			if(pattern[j]!=text[i+j]){
+				found = false;
+				break;
+			}
+		}
+		if(found)
+			ans.push_back(i);
+	}
+	return ans;
+}
+int main(){
+
+	string text = "Hey there! this is a text string, within which we wanna search a pattern.  \
+	Note that pattern repeats itself, so search for pattern if you wanna see can this report multiple occurrences of pattern.";
+	string pattern = "pattern";
+	vector<int> indices = linearSearch(text,pattern);
+	for(auto i:indices){
+		cout<<i<<",";
+	}
+}