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March 29, 2025 16:26
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You are given an array nums of n positive integers and an integer k. Initially, you start with a score of 1. You have to maximize your score by applying the following operation at most k times: Choose any non-empty subarray nums[l, ..., r] that you
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/** | |
* @param {number[]} nums | |
* @param {number} k | |
* @return {number} | |
*/ | |
// A class to handle modular arithmetic operations | |
class Modulo { | |
constructor(modulo) { | |
this.modulo = modulo; // The modulus for all operations | |
this._phi = modulo - 1; // Euler's totient function for primes (modulo is prime) | |
} | |
// Get the precomputed value of Euler's totient function | |
getPhi() { | |
return this._phi; | |
} | |
// Compute the modular inverse of 'a' under the current modulus | |
getInverse(a) { | |
return this.pow(a, this.getPhi() - 1); // Using Fermat's little theorem | |
} | |
// Add multiple numbers under the modulus | |
add(...numbers) { | |
let result = 0; | |
for (let number of numbers) { | |
result = (result + (number % this.modulo)) % this.modulo; // Add numbers modulo | |
} | |
if (result < 0) result += this.modulo; // Handle negative results | |
return result; | |
} | |
// Efficiently compute (a * b) % modulo using repeated addition | |
_quickMul(a, b) { | |
a = ((a % this.modulo) + this.modulo) % this.modulo; // Normalize 'a' | |
b = ((b % this.modulo) + this.modulo) % this.modulo; // Normalize 'b' | |
if (a === 0 || b === 0) return 0; // Multiplication with zero | |
let result = 0; | |
while (b) { | |
while (b % 2 === 0) { // When 'b' is even, double 'a' and halve 'b' | |
a = (a * 2) % this.modulo; | |
b /= 2; | |
} | |
if (b % 2 !== 0) { // Add 'a' to the result if 'b' is odd | |
result = (result + a) % this.modulo; | |
b--; | |
} | |
} | |
return result; | |
} | |
// Multiply multiple numbers under the modulus | |
mul(...numbers) { | |
let result = 1; | |
for (let number of numbers) { | |
if (number > 0 && number < 1) // Handle fractions by computing modular inverse | |
number = this.getInverse(Math.round(1 / number)); | |
result = this._quickMul(result, number); // Multiply with modular arithmetic | |
if (result === 0) return 0; // Stop early if result is zero | |
} | |
if (result < 0) result += this.modulo; // Handle negative results | |
return result; | |
} | |
// Divide 'a' by 'b' under the modulus (a / b % modulo) | |
div(a, b) { | |
return this._quickMul(a, this.getInverse(b)); // Multiply by modular inverse of 'b' | |
} | |
// Compute (a^b) % modulo using modular exponentiation | |
pow(a, b) { | |
a = ((a % this.modulo) + this.modulo) % this.modulo; // Normalize 'a' | |
if (a === 0) return 0; // Zero to any power is zero | |
let result = 1; | |
while (b) { | |
while (b % 2 === 0) { // When 'b' is even, square 'a' and halve 'b' | |
a = this._quickMul(a, a); | |
b /= 2; | |
} | |
if (b % 2 !== 0) { // Multiply 'result' by 'a' if 'b' is odd | |
result = this._quickMul(result, a); | |
b--; | |
} | |
} | |
return result; | |
} | |
} | |
// Initialize modular arithmetic with modulo 1e9+7 | |
const mod = new Modulo(1000000007); | |
// Initialize the Sieve of Eratosthenes to count prime factors for numbers up to 'n' | |
function initEratosthenesSieve(n) { | |
let eratosthenesSieve = Array(n + 1).fill(0); // Array to store counts of prime factors | |
eratosthenesSieve[1] = 0; // 1 has no prime factors | |
for (let i = 2; i <= n; i++) { | |
if (!eratosthenesSieve[i]) { // 'i' is prime if its count is still 0 | |
for (let j = i; j <= n; j += i) { // Increment counts for multiples of 'i' | |
eratosthenesSieve[j]++; | |
} | |
} | |
} | |
return eratosthenesSieve; | |
} | |
// Precompute the prime factor counts for numbers up to 100,000 | |
let eratosthenesSieve = initEratosthenesSieve(100000); | |
// Function to calculate the maximum score | |
var maximumScore = function (nums, k) { | |
const n = nums.length; // Length of the array | |
const pre = Array(n).fill(0); // Array to store previous lower-priority indices | |
const pos = Array(n).fill(n); // Array to store next higher-priority indices | |
// Helper function to compare priority based on prime factor count | |
function isMorePriority(l, r) { | |
return eratosthenesSieve[nums[l]] >= eratosthenesSieve[nums[r]]; | |
} | |
let st = []; // Stack for finding previous lower-priority indices | |
for (let i = 0; i < n; i++) { | |
while (st.length && !isMorePriority(st[st.length - 1], i)) st.pop(); | |
pre[i] = st.length ? st[st.length - 1] : -1; // Update 'pre' array | |
st.push(i); | |
} | |
st = []; // Stack for finding next higher-priority indices | |
for (let i = n - 1; i >= 0; i--) { | |
while (st.length && isMorePriority(i, st[st.length - 1])) st.pop(); | |
pos[i] = st.length ? st[st.length - 1] : n; // Update 'pos' array | |
st.push(i); | |
} | |
// Sort indices by element values in descending order | |
const indices = Array.from(Array(n), (_, i) => i); | |
indices.sort((a, b) => nums[b] - nums[a]); | |
let result = 1; // Initial score | |
for (let i = 0; i < n; i++) { | |
const ind = indices[i]; // Current index | |
const pow = Math.min((ind - pre[ind]) * (pos[ind] - ind), k); // Maximum power usable for this element | |
result = mod.mul(result, mod.pow(nums[ind], pow)); // Update result using modular multiplication | |
k -= pow; // Decrease remaining operations | |
if (!k) return result; // Stop if no operations are left | |
} | |
}; |
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