Add Recursion and Backtracking

Aaliyah Beg/Basics of Programming/Getting Started/PrimeFactorizationOfANumber.cpp

@@ -22,6 +22,8 @@ using namespace std;
 //     return 0;
 // }
 //print prime factorization
+
+//spf:smallest prime factor
 int main(){
     int n;cin>>n;
     int spf[n+1];

Aaliyah Beg/Basics of Programming/Getting Started/RotateANumber.cpp

@@ -5,11 +5,11 @@ int main() {
     string n;
     cin>>n>>k;
     int k_new=abs(k)%n.length();
-    if(k_new<0){
-        cout<<n.substr(k_new-1)+n.substr(0,k_new-1);
+    if(k<0){
+        cout<<n.substr(k_new)+n.substr(0,k_new);
     }
-    else if(k_new>0){
-        cout<<n.substr(n.length()- k_new + 1)+n.substr(0,n.length()- k_new + 1);
+    else if(k>0){
+        cout<<n.substr(n.length()- k_new )+n.substr(0,n.length()- k_new );
     }
     else{
         cout<<n;

Aaliyah Beg/Recursion and backtracking/.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+    "files.associations": {
+        "iostream": "cpp"
+    }
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/Factorial.cpp

@@ -0,0 +1,12 @@
+#include<bits/stdc++.h>
+using namespace std;
+int fac(int n){
+    //base case
+    if(n==1) return 1;
+    return n*fac(n-1);
+}
+int main(){
+    int n;cin>>n;
+    cout<<fac(n);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/Powerlinear.cpp

@@ -0,0 +1,13 @@
+#include<bits/stdc++.h>
+using namespace std;
+int powerlinear(int x,int n){
+    //base case
+    if(n==0) return 1;
+    return x* powerlinear(x,n-1);
+}
+int main(){
+    int x;cin>>x;
+    int n;cin>>n;
+    cout<<powerlinear(x,n);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/Powerlogarithmic.cpp

@@ -0,0 +1,17 @@
+#include<bits/stdc++.h>
+using namespace std;
+int powerlogrithmic(int x,int n){
+    //base case
+    if(n==0) return 1;
+    //recursive case
+    if(n%2==0)
+    return x*x*powerlogrithmic(x,n/2-1)*powerlogrithmic(x,n/2-1);
+    else
+    return x*powerlogrithmic(x,n/2)*powerlogrithmic(x,n/2);
+}
+int main(){
+    int x;cin>>x;
+    int n;cin>>n;
+    cout<<powerlogrithmic(x,n);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/Printdecreasing.cpp

@@ -0,0 +1,14 @@
+#include<bits/stdc++.h>
+using namespace std;
+void printdecreasing(int n){
+    //base case
+    if(n==0) return;
+    cout<<n<<"\n";
+    printdecreasing(n-1);
+    return;
+}
+int main(){
+    int n;cin>>n;
+    printdecreasing(n);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/TowerOfhanoi.cpp

@@ -0,0 +1,20 @@
+#include<bits/stdc++.h>
+using namespace std;
+void toh(int n,int a,int b,int c){
+    //base case
+    if(n==0) return;
+    //recursive case
+    toh(n-1,a,c,b);
+    cout<<n<<"["<<a<<"->"<<b<<"] \n";
+    toh(n-1,c,b,a);
+    return;
+
+}
+int main(){
+    int n;cin>>n;
+    int a;cin>>a;
+    int b;cin>>b;
+    int c;cin>>c;
+    toh(n,a,b,c);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/printincreasing.cpp

@@ -0,0 +1,15 @@
+#include<bits/stdc++.h>
+using namespace std;
+void printincreasing(int n){
+    //base case
+    if(n==0) return;
+
+    printincreasing(n-1);
+    cout<<n<<"\n";
+    return;
+}
+int main(){
+    int n;cin>>n;
+    printincreasing(n);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/printincreasingdecreasing.cpp

@@ -0,0 +1,15 @@
+#include<bits/stdc++.h>
+using namespace std;
+void printincreasingdecreasing(int n){
+    //base case
+    if(n==0) return;
+    cout<<n<<"\n";
+    printincreasingdecreasing(n-1);
+    cout<<n<<"\n";
+    return;
+}
+int main(){
+    int n;cin>>n;
+    printincreasingdecreasing(n);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Introduction to Recursion/printzigzag.cpp

@@ -0,0 +1,10 @@
+#include<bits/stdc++.h>
+using namespace std;
+void printzigzag(int n){
+
+}
+int main(){
+    int n;cin>>n;
+    printzigzag(n);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Recursion Backtracking/Floodfill.cpp

@@ -0,0 +1,62 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define pb push_back
+vector<string> floodfill(int a[][1000],bool v[][1000],int n,int m,int i,int j){
+
+    //base case
+    if( j==-1 || i==-1 || i==n || j==m || a[i][j]==1 || v[i][j]==true){
+        vector<string>base_ans;
+        return base_ans;
+    }
+    if(i==n-1 && j==m-1){
+        vector<string>base_ans;
+        base_ans.pb("");
+        return base_ans;
+    }
+    //recursive case
+    vector<string>bada_ans;
+    v[i][j]=true;
+    vector<string>chota_ans1=floodfill(a,v,n,m,i-1,j);
+
+    for(auto x:chota_ans1){
+        bada_ans.pb('u'+x);
+    }
+    vector<string>chota_ans2=floodfill(a,v,n,m,i+1,j);
+
+    for(auto x:chota_ans2){
+        bada_ans.pb('d'+x);
+    }
+    vector<string>chota_ans3=floodfill(a,v,n,m,i,j-1);
+
+    for(auto x:chota_ans3){
+        bada_ans.pb('l'+x);
+    }
+    vector<string>chota_ans4=floodfill(a,v,n,m,i,j+1);
+
+    for(auto x:chota_ans4){
+        bada_ans.pb('r'+x);
+    }
+    v[i][j]=false;
+
+    return bada_ans;
+}
+int main(){
+    int n,m;
+    cin>>n>>m;
+    int a[1000][1000];
+    bool v[1000][1000];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<m;j++){
+            cin>>a[i][j];
+            v[i][j]=false;
+        }
+    }
+    // int b=n-1;
+    // int c=m-1;
+    vector<string>ans=floodfill(a,v,n,m,0,0);
+
+    for(auto x:ans){
+        cout<<x<<"\n";
+    }
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Recursion Backtracking/Floodfill_2.cpp

@@ -0,0 +1,41 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define pb push_back
+void floodfill(int a[][1000],bool v[][1000],int n,int m,int i,int j,string psf){
+    //base case
+    if( j==-1 || i==-1 || i==n || j==m || a[i][j]==1 || v[i][j]==true){
+        return;
+    }
+    if(i==n-1 && j==m-1){
+        cout<<psf<<"\n";
+        return;
+    }
+    //recursive case
+
+    v[i][j]=true;
+    floodfill(a,v,n,m,i-1,j,psf+'u');
+    floodfill(a,v,n,m,i+1,j,psf+'d');
+    floodfill(a,v,n,m,i,j-1,psf+'l');
+    floodfill(a,v,n,m,i,j+1,psf+'r');
+    v[i][j]=false;
+    return;
+
+}
+int main(){
+    int n,m;
+    cin>>n>>m;
+    int a[1000][1000];
+    bool v[1000][1000];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<m;j++){
+            cin>>a[i][j];
+            v[i][j]=false;
+        }
+    }
+    // int b=n-1;
+    // int c=m-1;
+
+    string psf;
+    floodfill(a,v,n,m,0,0,psf);
+    return 0;
+}

Aaliyah Beg/Recursion and backtracking/Recursion Backtracking/Knightstour.cpp

@@ -0,0 +1,46 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define pb push_back
+void knightstour(int a[1000][1000],int n,int r,int c,int step){
+    //base case
+    if(r<0 || c<0 || r>=n || c>=n || a[r][c]!=0){
+        return ;
+    }
+    if(step==n*n) {
+        a[r][c]=step;
+        for(int i=0;i<n;i++){
+            for(int j=0;j<n;j++){
+                cout<<a[i][j]<<" ";
+            }
+            cout<<endl;
+        }
+        cout<<"\n-------------------------- \n";
+        a[r][c]=0;
+        return;
+    }
+    a[r][c]=step;
+    knightstour(a,n,r-2,c+1,step+1);
+    knightstour(a,n,r-1,c+2,step+1);
+    knightstour(a,n,r+1,c+2,step+1);
+    knightstour(a,n,r+2,c+1,step+1);
+    knightstour(a,n,r+2,c-1,step+1);
+    knightstour(a,n,r+1,c-2,step+1);
+    knightstour(a,n,r-1,c-2,step+1);
+    knightstour(a,n,r-2,c-1,step+1);
+    a[r][c]=0;
+    return;
+
+
+}
+int main(){
+    int n;cin>>n;
+    int r;cin>>r;
+    int c;cin>>c;
+    int a[1000][1000];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<n;j++){
+            a[i][j]=0;
+        }
+    }
+    knightstour(a,n,r,c,1);
+}

Aaliyah Beg/Recursion and backtracking/Recursion Backtracking/Nqueens.cpp

@@ -0,0 +1,58 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define pb push_back
+bool check(int a[1000][1000],int i,int j,int n){
+    for(int x=i-1;x>-1;x--){
+
+        if(a[x][j]==1){
+            return false;
+        }
+    }
+    for(int x=1;x<=i and x<=j;x++){
+        if(a[i-x][j-x]==1){
+            return false;
+        }
+    }
+    for(int x=1;x<=i and x<n-j;x++){
+        if(a[i-x][j+x]==1){
+            return false;
+        }
+    }
+    return true;
+}
+
+void Nqueens(int a[1000][1000],int n,int i){
+    //base case
+    if(i==n){
+        for(int i=0;i<n;i++){
+            for(int j=0;j<n;j++){
+                cout<<a[i][j]<<" ";
+            }
+            cout<<"\n";
+        }
+        return;
+    }
+    for(int j=0;j<n;j++){
+        if(check(a,i,j,n)){
+            a[i][j]=1;
+            Nqueens(a,n,i+1);
+            a[i][j]=0;
+        }
+    }
+    return;
+}
+// recursion ka tree visulaize karte hain usmein 
+//left mein pre written cheez hoti hai when we are going down
+//phir recursive call
+//phir right mein post written cheez hoti hai when we are going up
+int main(){
+    int n;cin>>n;
+    int ans[1000][1000];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<n;j++){
+            ans[i][j]=0;
+        }
+    }
+    Nqueens(ans,n,0);
+    return 0;
+}