Recursion exercises and maze resolution with backtracking

theory/recursion/binary_search.cpp

@@ -0,0 +1,37 @@
+#include <iostream>
+#include <vector>
+
+
+int binary_search(int *v, int l, int r, int x) {
+
+    int m = (l+r)/2;
+
+    // base cases
+    if(v[m] == x)
+        return m;
+
+    if(l > r)
+        return -1;
+
+    // recursion call
+    if(v[m] < x )
+        return binary_search(v,m+1,r,x);
+    else
+        return binary_search(v,l,m-1,x);
+
+}
+
+
+int main(){
+
+    int vet[] = {0,1,2,3,4,5,6,7,8,9};
+    int n = 10;
+    int v = binary_search(vet,0,n-1,8);
+
+    if(v != -1)
+        std::cout << "found at index: " << v << std::endl;
+    else
+        std::cout << "not found" << std::endl;
+
+}
+

theory/recursion/level1_questions.cpp

@@ -0,0 +1,222 @@
+#include <iostream>
+#include <string>
+#include <cstring>
+#include <algorithm>
+
+/*
+    Question 1:
+
+    Give an integer N, print all the number before N
+    until 1;
+
+    input: 5
+
+    output: 5 4 3 2 1
+*/
+void print_until_n(int n) {
+
+    // base case
+    if(n == 1) {
+        std::cout << 1 << std::endl;
+        return;
+    }
+
+    // recursion call
+    std::cout << n << " ";
+    print_until_n(n-1);
+
+}
+
+
+/*
+    Question 2:
+
+    Print all the number between [1,N];
+
+    input: 5
+
+    output: 1 2 3 4 5
+*/
+void print_at_n(int n) {
+
+    // base case
+    if(n == 1) {
+        std::cout << 1 << " ";
+        return;
+    }
+
+    // recursion call
+    print_at_n(n-1);
+    std::cout << n << " ";
+
+}
+
+/*
+    Question 3:
+
+    Factorial of a number N;
+*/
+int factorial(int n) {
+
+    // base case
+    if(n==1)
+        return 1;
+
+    // recursion case
+    return n*factorial(n-1);
+
+}
+
+/*
+    Question 4:
+
+    Sum of the digit between [N,1];
+
+
+*/
+int sum_between_n(int n) {
+
+    // base case
+    if(n == 1)
+        return 1;
+
+    // recursion call
+    return n+sum_between_n(n-1);
+
+}
+
+/*
+    Question 5:
+
+    sum of digits of N
+
+*/
+int sum_of_digits(int n) {
+
+    // base case
+    if (n/10 == 0)
+        return n;
+
+    // recursion call
+    return n%10+sum_of_digits(n/10); 
+
+}
+
+/*
+    Question 6:
+
+    Products of digits of N;
+*/
+int products_of_n(int n) {
+
+    // base case
+    if(n/10 == 0)
+        return n;
+
+    // recursion call
+    return n%10*products_of_n(n/10);
+
+}
+
+/*
+    Question 7:
+
+    reverse a number N;
+*/
+void reverse(int n) {
+
+    // base case
+    if(n/10 == 0) {
+        std::cout << n;
+        return;
+    }
+
+    std::cout << n%10;
+    reverse(n/10);
+
+}
+
+/*
+    Question 8:
+
+    Check if N is a palindrome
+*/
+bool palindrome(std::string n) {
+
+    std::string n2;
+    for(int i = n.length(), b = 0; i >= 0; --i, ++b)
+        n2[b] = n[i];
+
+    if(n2 == n)
+        return true;
+    else 
+        return false; 
+
+}
+
+
+
+
+
+
+int main(){
+
+    std::cout << "Question 01" << std::endl;
+    print_until_n(5);
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 02" << std::endl;
+    print_at_n(5);
+    std::cout << std::endl;
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 03" << std::endl;
+    std::cout << factorial(5) << std::endl;
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 04" << std::endl;
+    std::cout << sum_between_n(10) << std::endl;
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 05" << std::endl;
+    std::cout << sum_of_digits(123) << std::endl;
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 06" << std::endl;
+    std::cout << products_of_n(222) << std::endl;
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 07" << std::endl;
+    reverse(345);
+    std::cout << std::endl;
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 08" << std::endl;
+    if(palindrome("123321"))
+        std::cout << "Is a palindrome" << std::endl;
+    else
+        std::cout << "Isn't a palindrome" << std::endl;
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 09" << std::endl;
+
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 10" << std::endl;
+
+    std::cout << std::endl;
+// ----------------------------------------------------
+    std::cout << "Question 11" << std::endl;
+
+    std::cout << std::endl;
+// ----------------------------------------------------
+
+
+}
+
+
+
+
+
+
+