# Competitive Programming Algorithms Every Beginner Must Know

`int binarySearch(int arr[], int l, int r, int x){if (r >= l) {int mid = l + (r - l) / 2if (arr[mid] == x)return mid;if (arr[mid] > x)return binarySearch(arr, l, mid - 1, x);return binarySearch(arr, mid + 1, r, x);}return -1;}`
`int binary_exponentiation(int a, int b){    if(b==0) return 1;    long long int value=binary_exponentiation(a,b/2);    if(b%2==0)    {        return value*value;    }    else    {        return a*value*value;    }}` A truth table illustrating the results on applying the said operators
`if(n%2 ! = 0) print(“ODD”);`
`if(n&1) print(“ODD”);`
`void SieveOfEratosthenes(int n){    bool prime[n + 1];    memset(prime, true, sizeof(prime));    for (int p = 2; p * p <= n; p++)    {        if (prime[p] == true)        {             for (int i = p * p; i <= n; i += p)                 prime[i] = false;        }}for (int p = 2; p <= n; p++)if (prime[p])cout << p << " ";}`

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