Donades les consultes Q del tipus: L R per a cada consulta cal imprimir el nombre màxim de divisors que un nombre x (L<= x <= R) té.
Exemples:
L = 1 R = 10 : 1 has 1 divisor. 2 has 2 divisors. 3 has 2 divisors. 4 has 3 divisors. 5 has 2 divisors. 6 has 4 divisors. 7 has 2 divisors. 8 has 4 divisors. 9 has 3 divisors. 10 has 4 divisors. So the answer for above query is 4 as it is the maximum number of divisors a number has in [1 10].
Requisits previs: Tamís Eratòstenes Arbre de segments
A continuació es mostren els passos per resoldre el problema.
Com trobar números bloquejats a Android
- En primer lloc, veurem quants nombres de divisors fa un nombre n = p1k1* pàg2k2* ... * pàgnkn (on pàg1pàg2... pàgnsón nombres primers) té; la resposta és (k1+ 1)*(k2+ 1)*...*(kn+ 1) . Com? Per a cada nombre primer de la factorització primer podem tenir el seu ki+ 1 possibles potències en un divisor (0 1 2... ki).
- Ara anem a veure com podem trobar la factorització primeres d'un nombre, primer construïm una matriu primer_menor[] que emmagatzema el divisor primer més petit de i a les ith índex dividim un nombre pel seu divisor primer més petit per obtenir un nou nombre (també tenim el divisor primer més petit d'aquest nou nombre emmagatzemat) seguim fent-ho fins que canvia el primer més petit del nombre quan el factor primer més petit del nou nombre és diferent del nombre anterior tenim kiper la ithnombre primer en la factorització primer del nombre donat.
- Finalment obtenim el nombre de divisors de tots els nombres i els emmagatzemem en un arbre de segments que manté els nombres màxims dels segments. Responem a cada consulta consultant l'arbre de segments.
// A C++ implementation of the above idea to process // queries of finding a number with maximum divisors. #include using namespace std; #define maxn 1000005 #define INF 99999999 int smallest_prime[maxn]; int divisors[maxn]; int segmentTree[4 * maxn]; // Finds smallest prime factor of all numbers in // range[1 maxn) and stores them in smallest_prime[] // smallest_prime[i] should contain the smallest prime // that divides i void findSmallestPrimeFactors() { // Initialize the smallest_prime factors of all // to infinity for (int i = 0 ; i < maxn ; i ++ ) smallest_prime[i] = INF; // to be built like eratosthenes sieve for (long long i = 2; i < maxn; i++) { if (smallest_prime[i] == INF) { // prime number will have its smallest_prime // equal to itself smallest_prime[i] = i; for (long long j = i * i; j < maxn; j += i) // if 'i' is the first prime number reaching 'j' if (smallest_prime[j] > i) smallest_prime[j] = i; } } } // number of divisors of n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) // are equal to (k1+1) * (k2+1) ... (kn+1) // this function finds the number of divisors of all numbers // in range [1 maxn) and stores it in divisors[] // divisors[i] stores the number of divisors i has void buildDivisorsArray() { for (int i = 1; i < maxn; i++) { divisors[i] = 1; int n = i p = smallest_prime[i] k = 0; // we can obtain the prime factorization of the number n // n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) using the // smallest_prime[] array we keep dividing n by its // smallest_prime until it becomes 1 whilst we check // if we have need to set k zero while (n > 1) { n = n / p; k ++; if (smallest_prime[n] != p) { //use p^k initialize k to 0 divisors[i] = divisors[i] * (k + 1); k = 0; } p = smallest_prime[n]; } } } // builds segment tree for divisors[] array void buildSegtmentTree(int node int a int b) { // leaf node if (a == b) { segmentTree[node] = divisors[a]; return ; } //build left and right subtree buildSegtmentTree(2 * node a (a + b) / 2); buildSegtmentTree(2 * node + 1 ((a + b) / 2) + 1 b); //combine the information from left //and right subtree at current node segmentTree[node] = max(segmentTree[2 * node] segmentTree[2 *node + 1]); } //returns the maximum number of divisors in [l r] int query(int node int a int b int l int r) { // If current node's range is disjoint with query range if (l > b || a > r) return -1; // If the current node stores information for the range // that is completely inside the query range if (a >= l && b <= r) return segmentTree[node]; // Returns maximum number of divisors from left // or right subtree return max(query(2 * node a (a + b) / 2 l r) query(2 * node + 1 ((a + b) / 2) + 1 blr)); } // driver code int main() { // First find smallest prime divisors for all // the numbers findSmallestPrimeFactors(); // Then build the divisors[] array to store // the number of divisors buildDivisorsArray(); // Build segment tree for the divisors[] array buildSegtmentTree(1 1 maxn - 1); cout << 'Maximum divisors that a number has ' << ' in [1 100] are ' << query(1 1 maxn - 1 1 100) << endl; cout << 'Maximum divisors that a number has' << ' in [10 48] are ' << query(1 1 maxn - 1 10 48) << endl; cout << 'Maximum divisors that a number has' << ' in [1 10] are ' << query(1 1 maxn - 1 1 10) << endl; return 0; }
Java // Java implementation of the above idea to process // queries of finding a number with maximum divisors. import java.util.*; class GFG { static int maxn = 10005; static int INF = 999999; static int []smallest_prime = new int[maxn]; static int []divisors = new int[maxn]; static int []segmentTree = new int[4 * maxn]; // Finds smallest prime factor of all numbers // in range[1 maxn) and stores them in // smallest_prime[] smallest_prime[i] should // contain the smallest prime that divides i static void findSmallestPrimeFactors() { // Initialize the smallest_prime factors // of all to infinity for (int i = 0 ; i < maxn ; i ++ ) smallest_prime[i] = INF; // to be built like eratosthenes sieve for (int i = 2; i < maxn; i++) { if (smallest_prime[i] == INF) { // prime number will have its // smallest_prime equal to itself smallest_prime[i] = i; for (int j = i * i; j < maxn; j += i) // if 'i' is the first // prime number reaching 'j' if (smallest_prime[j] > i) smallest_prime[j] = i; } } } // number of divisors of n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) // are equal to (k1+1) * (k2+1) ... (kn+1) // this function finds the number of divisors of all numbers // in range [1 maxn) and stores it in divisors[] // divisors[i] stores the number of divisors i has static void buildDivisorsArray() { for (int i = 1; i < maxn; i++) { divisors[i] = 1; int n = i p = smallest_prime[i] k = 0; // we can obtain the prime factorization of // the number n n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) // using the smallest_prime[] array we keep dividing n // by its smallest_prime until it becomes 1 // whilst we check if we have need to set k zero while (n > 1) { n = n / p; k ++; if (smallest_prime[n] != p) { // use p^k initialize k to 0 divisors[i] = divisors[i] * (k + 1); k = 0; } p = smallest_prime[n]; } } } // builds segment tree for divisors[] array static void buildSegtmentTree(int node int a int b) { // leaf node if (a == b) { segmentTree[node] = divisors[a]; return ; } //build left and right subtree buildSegtmentTree(2 * node a (a + b) / 2); buildSegtmentTree(2 * node + 1 ((a + b) / 2) + 1 b); //combine the information from left //and right subtree at current node segmentTree[node] = Math.max(segmentTree[2 * node] segmentTree[2 *node + 1]); } // returns the maximum number of divisors in [l r] static int query(int node int a int b int l int r) { // If current node's range is disjoint // with query range if (l > b || a > r) return -1; // If the current node stores information // for the range that is completely inside // the query range if (a >= l && b <= r) return segmentTree[node]; // Returns maximum number of divisors from left // or right subtree return Math.max(query(2 * node a (a + b) / 2 l r) query(2 * node + 1 ((a + b) / 2) + 1 b l r)); } // Driver Code public static void main(String[] args) { // First find smallest prime divisors // for all the numbers findSmallestPrimeFactors(); // Then build the divisors[] array to store // the number of divisors buildDivisorsArray(); // Build segment tree for the divisors[] array buildSegtmentTree(1 1 maxn - 1); System.out.println('Maximum divisors that a number ' + 'has in [1 100] are ' + query(1 1 maxn - 1 1 100)); System.out.println('Maximum divisors that a number ' + 'has in [10 48] are ' + query(1 1 maxn - 1 10 48)); System.out.println('Maximum divisors that a number ' + 'has in [1 10] are ' + query(1 1 maxn - 1 1 10)); } } // This code is contributed by PrinciRaj1992
Python 3 # Python 3 implementation of the above # idea to process queries of finding a # number with maximum divisors. maxn = 1000005 INF = 99999999 smallest_prime = [0] * maxn divisors = [0] * maxn segmentTree = [0] * (4 * maxn) # Finds smallest prime factor of all # numbers in range[1 maxn) and stores # them in smallest_prime[] smallest_prime[i] # should contain the smallest prime that divides i def findSmallestPrimeFactors(): # Initialize the smallest_prime # factors of all to infinity for i in range(maxn ): smallest_prime[i] = INF # to be built like eratosthenes sieve for i in range(2 maxn): if (smallest_prime[i] == INF): # prime number will have its # smallest_prime equal to itself smallest_prime[i] = i for j in range(i * i maxn i): # if 'i' is the first prime # number reaching 'j' if (smallest_prime[j] > i): smallest_prime[j] = i # number of divisors of n = (p1 ^ k1) * # (p2 ^ k2) ... (pn ^ kn) are equal to # (k1+1) * (k2+1) ... (kn+1). This function # finds the number of divisors of all numbers # in range [1 maxn) and stores it in divisors[] # divisors[i] stores the number of divisors i has def buildDivisorsArray(): for i in range(1 maxn): divisors[i] = 1 n = i p = smallest_prime[i] k = 0 # we can obtain the prime factorization # of the number n n = (p1 ^ k1) * (p2 ^ k2) # ... (pn ^ kn) using the smallest_prime[] # array we keep dividing n by its # smallest_prime until it becomes 1 whilst # we check if we have need to set k zero while (n > 1): n = n // p k += 1 if (smallest_prime[n] != p): # use p^k initialize k to 0 divisors[i] = divisors[i] * (k + 1) k = 0 p = smallest_prime[n] # builds segment tree for divisors[] array def buildSegtmentTree( node a b): # leaf node if (a == b): segmentTree[node] = divisors[a] return #build left and right subtree buildSegtmentTree(2 * node a (a + b) // 2) buildSegtmentTree(2 * node + 1 ((a + b) // 2) + 1 b) #combine the information from left #and right subtree at current node segmentTree[node] = max(segmentTree[2 * node] segmentTree[2 * node + 1]) # returns the maximum number of # divisors in [l r] def query(node a b l r): # If current node's range is disjoint # with query range if (l > b or a > r): return -1 # If the current node stores information # for the range that is completely inside # the query range if (a >= l and b <= r): return segmentTree[node] # Returns maximum number of divisors # from left or right subtree return max(query(2 * node a (a + b) // 2 l r) query(2 * node + 1 ((a + b) // 2) + 1 b l r)) # Driver code if __name__ == '__main__': # First find smallest prime divisors # for all the numbers findSmallestPrimeFactors() # Then build the divisors[] array to # store the number of divisors buildDivisorsArray() # Build segment tree for the divisors[] array buildSegtmentTree(1 1 maxn - 1) print('Maximum divisors that a number has ' ' in [1 100] are ' query(1 1 maxn - 1 1 100)) print('Maximum divisors that a number has' ' in [10 48] are ' query(1 1 maxn - 1 10 48)) print( 'Maximum divisors that a number has' ' in [1 10] are ' query(1 1 maxn - 1 1 10)) # This code is contributed by ita_c
C# // C# implementation of the above idea // to process queries of finding a number // with maximum divisors. using System; class GFG { static int maxn = 10005; static int INF = 999999; static int []smallest_prime = new int[maxn]; static int []divisors = new int[maxn]; static int []segmentTree = new int[4 * maxn]; // Finds smallest prime factor of all numbers // in range[1 maxn) and stores them in // smallest_prime[] smallest_prime[i] should // contain the smallest prime that divides i static void findSmallestPrimeFactors() { // Initialize the smallest_prime // factors of all to infinity for (int i = 0 ; i < maxn ; i ++ ) smallest_prime[i] = INF; // to be built like eratosthenes sieve for (int i = 2; i < maxn; i++) { if (smallest_prime[i] == INF) { // prime number will have its // smallest_prime equal to itself smallest_prime[i] = i; for (int j = i * i; j < maxn; j += i) // if 'i' is the first // prime number reaching 'j' if (smallest_prime[j] > i) smallest_prime[j] = i; } } } // number of divisors of // n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) // are equal to (k1+1) * (k2+1) ... (kn+1) // this function finds the number of divisors // of all numbers in range [1 maxn) and stores // it in divisors[] divisors[i] stores the // number of divisors i has static void buildDivisorsArray() { for (int i = 1; i < maxn; i++) { divisors[i] = 1; int n = i p = smallest_prime[i] k = 0; // we can obtain the prime factorization of // the number n // n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) // using the smallest_prime[] array // we keep dividing n by its smallest_prime // until it becomes 1 whilst we check if // we have need to set k zero while (n > 1) { n = n / p; k ++; if (smallest_prime[n] != p) { // use p^k initialize k to 0 divisors[i] = divisors[i] * (k + 1); k = 0; } p = smallest_prime[n]; } } } // builds segment tree for divisors[] array static void buildSegtmentTree(int node int a int b) { // leaf node if (a == b) { segmentTree[node] = divisors[a]; return; } //build left and right subtree buildSegtmentTree(2 * node a (a + b) / 2); buildSegtmentTree(2 * node + 1 ((a + b) / 2) + 1 b); //combine the information from left //and right subtree at current node segmentTree[node] = Math.Max(segmentTree[2 * node] segmentTree[2 *node + 1]); } // returns the maximum number of divisors in [l r] static int query(int node int a int b int l int r) { // If current node's range is disjoint // with query range if (l > b || a > r) return -1; // If the current node stores information // for the range that is completely inside // the query range if (a >= l && b <= r) return segmentTree[node]; // Returns maximum number of divisors from left // or right subtree return Math.Max(query(2 * node a (a + b) / 2 l r) query(2 * node + 1 ((a + b) / 2) + 1 b l r)); } // Driver Code public static void Main(String[] args) { // First find smallest prime divisors // for all the numbers findSmallestPrimeFactors(); // Then build the divisors[] array // to store the number of divisors buildDivisorsArray(); // Build segment tree for the divisors[] array buildSegtmentTree(1 1 maxn - 1); Console.WriteLine('Maximum divisors that a number ' + 'has in [1 100] are ' + query(1 1 maxn - 1 1 100)); Console.WriteLine('Maximum divisors that a number ' + 'has in [10 48] are ' + query(1 1 maxn - 1 10 48)); Console.WriteLine('Maximum divisors that a number ' + 'has in [1 10] are ' + query(1 1 maxn - 1 1 10)); } } // This code is contributed by 29AjayKumar
JavaScript <script> // JavaScript implementation of the above idea to process // queries of finding a number with maximum divisors. let maxn = 10005; let INF = 999999; let smallest_prime = new Array(maxn); for(let i=0;i<maxn;i++) { smallest_prime[i]=0; } let divisors = new Array(maxn); for(let i=0;i<maxn;i++) { divisors[i]=0; } let segmentTree = new Array(4 * maxn); for(let i=0;i<4*maxn;i++) { segmentTree[i]=0; } // Finds smallest prime factor of all numbers // in range[1 maxn) and stores them in // smallest_prime[] smallest_prime[i] should // contain the smallest prime that divides i function findSmallestPrimeFactors() { // Initialize the smallest_prime factors // of all to infinity for (let i = 0 ; i < maxn ; i ++ ) smallest_prime[i] = INF; // to be built like eratosthenes sieve for (let i = 2; i < maxn; i++) { if (smallest_prime[i] == INF) { // prime number will have its // smallest_prime equal to itself smallest_prime[i] = i; for (let j = i * i; j < maxn; j += i) { // if 'i' is the first // prime number reaching 'j' if (smallest_prime[j] > i) smallest_prime[j] = i; } } } } // number of divisors of n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) // are equal to (k1+1) * (k2+1) ... (kn+1) // this function finds the number of divisors of all numbers // in range [1 maxn) and stores it in divisors[] // divisors[i] stores the number of divisors i has function buildDivisorsArray() { for (let i = 1; i < maxn; i++) { divisors[i] = 1; let n = i; let p = smallest_prime[i] let k = 0; // we can obtain the prime factorization of // the number n n = (p1 ^ k1) * (p2 ^ k2) ... (pn ^ kn) // using the smallest_prime[] array we keep dividing n // by its smallest_prime until it becomes 1 // whilst we check if we have need to set k zero while (n > 1) { n = Math.floor(n / p); k++; if (smallest_prime[n] != p) { // use p^k initialize k to 0 divisors[i] = divisors[i] * (k + 1); k = 0; } p = smallest_prime[n]; } } } // builds segment tree for divisors[] array function buildSegtmentTree(nodeab) { // leaf node if (a == b) { segmentTree[node] = divisors[a]; return ; } //build left and right subtree buildSegtmentTree(2 * node a Math.floor((a + b) / 2)); buildSegtmentTree((2 * node) + 1 Math.floor((a + b) / 2) + 1 b); //combine the information from left //and right subtree at current node segmentTree[node] = Math.max(segmentTree[2 * node] segmentTree[(2 *node) + 1]); } // returns the maximum number of divisors in [l r] function query(nodeablr) { // If current node's range is disjoint // with query range if (l > b || a > r) return -1; // If the current node stores information // for the range that is completely inside // the query range if (a >= l && b <= r) return segmentTree[node]; // Returns maximum number of divisors from left // or right subtree return Math.max(query(2 * node a Math.floor((a + b) / 2) l r) query(2 * node + 1 Math.floor((a + b) / 2) + 1 b l r)); } // Driver Code // First find smallest prime divisors // for all the numbers findSmallestPrimeFactors(); // Then build the divisors[] array to store // the number of divisors buildDivisorsArray(); // Build segment tree for the divisors[] array buildSegtmentTree(1 1 maxn - 1); document.write('Maximum divisors that a number ' + 'has in [1 100] are ' + query(1 1 maxn - 1 1 100)+'
'); document.write('Maximum divisors that a number ' + 'has in [10 48] are ' + query(1 1 maxn - 1 10 48)+'
'); document.write('Maximum divisors that a number ' + 'has in [1 10] are ' + query(1 1 maxn - 1 1 10)+'
'); // This code is contributed by avanitrachhadiya2155 </script>
Sortida:
Maximum divisors that a number has in [1 100] are 12 Maximum divisors that a number has in [10 48] are 10 Maximum divisors that a number has in [1 10] are 4
Complexitat temporal: O((maxn + Q) * log (maxn))
executant scripts a linux
- Per al tamís: O(maxn * log(log(maxn)))
- Per calcular els divisors de cada nombre: D'acord1 + k2 + ... + kn) < O (log (màxn))
- Per consultar cada interval: O (log (màxn))
Espai auxiliar: O(n)
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