In this tutorial, we will be discussing a program to find the number of paths between two vertices.For this we will be provided with a directed graph. Our task is to find the number of paths possible between two given vertices.Example#include using namespace std; //constructing a directed graph class Graph{    int V;    list *adj;    void countPathsUtil(int, int, bool [], int &);    public:       //constructor       Graph(int V);       void addEdge(int u, int v);       int countPaths(int s, int d); }; Graph::Graph(int V){    this->V = V;    adj ... Read More

In this tutorial, we will be discussing a program to find the number of possible N digit numbers that satisfy the given condition.For this we will be provided with an integer. Our task is to check which one of number having N digits followNumber + Reverse(Number) = 10N -1Example#include using namespace std; //returning the count of numbers string count_num(int N){    if (N % 2 == 1)       return 0;    string result = "9";    for (int i = 1; i

In this tutorial, we will be discussing a program to find the number of possible groups of size 2 or 3 that have sum as multiple of 3.In this tutorial, we will be discussing a program to find the number of possible groups of size 2 or 3 that have sum as multiple of 3.Example#include using namespace std; //returning count of pairs of //2 or 3 int count_groups(int arr[], int n){    int c[3] = {0}, i;    int res = 0;    for (i=0; i>1);    res += c[1] * c[2];    res += (c[0] * (c[0]-1) * (c[0]-2))/6; ... Read More

In this tutorial, we will be discussing a program to find the number of all perfect divisors of a number.For this we will be provided with a number. Our task is to count all the perfect divisors of that given number.Example#include using namespace std; //checking perfect square bool if_psquare(int n){    int sq = (int) sqrt(n);    return (n == sq * sq); } //returning count of perfect divisors int count_pdivisors(int n){    int count = 0;    for (int i=1; i*i

In this tutorial, we will be discussing a program to find the number of all palindromic subsequences in a given string.For this we will be provided with a string. Our task is to find the number of palindromic subsequences that can be made in that given string.Example#include #include using namespace std; //returning total palindromic sequence int count_palin(string str){    int N = str.length();    //creating a 2D array    int cps[N+1][N+1];    memset(cps, 0 ,sizeof(cps));    for (int i=0; i

In this tutorial, we will be discussing a program to find the number of palindromes which are squares of a palindrome.For this we will be provided with two values L and R. Our task is to find the number of super palindromes in the given range. A super palindrome is the one in which the number and its square both are palindromes.Example#include using namespace std; //checking if the number is a palindrome bool if_palin(int x){    int ans = 0;    int temp = x;    while (temp > 0){       ans = 10 * ans + ... Read More

In this tutorial, we will be discussing a program to find the number of palindrome sub strings in a string.For this we will be given a string. Our task is to count the number of palindrome sub strings in the given string with length greater than 3.Example#include using namespace std; //counting palindrome strings int count_pstr(char str[], int n){    int dp[n][n];    memset(dp, 0, sizeof(dp));    bool P[n][n];    memset(P, false , sizeof(P));    for (int i= 0; i< n; i++)       P[i][i] = true;    for (int i=0; i

In this tutorial, we will be discussing a program to find the number of pairs with the given XOR.For this we will be provided with an array and a value. Our task is to find the number of pairs whose XOR is equal to the given value.Example#include using namespace std; //returning the number of pairs //having XOR equal to given value int count_pair(int arr[], int n, int x){    int result = 0;    //managing with duplicate values    unordered_map m;    for (int i=0; i

In this tutorial, we will be discussing a program to find the number of pairs of an array which differ in K bits.For this we will be provided with an array and an integer K. Our task is to find the number of pairs who differ by K bits in their binary representation.Example#include using namespace std; //counting number of bits in //binary representation int count_bit(int n){    int count = 0;    while (n) {       if (n & 1)          ++count;       n >>= 1;    }    return count; } ... Read More

In this tutorial, we will be discussing a program to find the number of pairs of adjacent nodes whose XOR is an odd number.For this we will be provided with a binary tree. Our task is to count the number of pairs of adjacent elements whose XOR is an odd number.Example Live Demo#include using namespace std; //node structure of tree struct Node {    int data;    struct Node *left, *right; }; //finding the pairs whose XOR //is odd int count_pair(Node* root, Node *parent=NULL){    if (root == NULL)       return 0;    //checking pair of XOR is ... Read More