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| 1 | +''' |
| 2 | +You are given an array nums of n positive integers and an integer k. |
| 3 | +
|
| 4 | +Initially, you start with a score of 1. You have to maximize your score by applying the following operation at most k times: |
| 5 | +
|
| 6 | +Choose any non-empty subarray nums[l, ..., r] that you haven't chosen previously. |
| 7 | +Choose an element x of nums[l, ..., r] with the highest prime score. If multiple such elements exist, choose the one with the smallest index. |
| 8 | +Multiply your score by x. |
| 9 | +Here, nums[l, ..., r] denotes the subarray of nums starting at index l and ending at the index r, both ends being inclusive. |
| 10 | +
|
| 11 | +The prime score of an integer x is equal to the number of distinct prime factors of x. For example, the prime score of 300 is 3 since 300 = 2 * 2 * 3 * 5 * 5. |
| 12 | +
|
| 13 | +Return the maximum possible score after applying at most k operations. |
| 14 | +
|
| 15 | +Since the answer may be large, return it modulo 109 + 7. |
| 16 | +''' |
| 17 | + |
| 18 | +#just sketch |
| 19 | +class Solution: |
| 20 | + def maximumScore(self, nums: List[int], k: int) -> int: |
| 21 | + n = len(nums) |
| 22 | + |
| 23 | + res = 1 |
| 24 | + |
| 25 | + #def prime_check().... |
| 26 | + |
| 27 | + for i in range(k): |
| 28 | + |
| 29 | + l = 0 |
| 30 | + |
| 31 | + r = n-1 |
| 32 | + |
| 33 | + while l<=r: |
| 34 | + sub = nums[l:r] |
| 35 | + |
| 36 | + l+=1 |
| 37 | + r-=1 |
| 38 | + |
| 39 | + for val in sub: |
| 40 | + temp= prime_check(val): |
| 41 | + if temp: |
| 42 | + res = max(res, temp) |
| 43 | + return res |
| 44 | + |
| 45 | +-------------------------------------------- |
| 46 | + |
| 47 | +class Solution: |
| 48 | + MOD = 10**9 + 7 |
| 49 | + |
| 50 | + def maximumScore(self, nums, k): |
| 51 | + n = len(nums) |
| 52 | + prime_scores = [0] * n |
| 53 | + |
| 54 | + # Calculate the prime score for each number in nums |
| 55 | + for index in range(n): |
| 56 | + num = nums[index] |
| 57 | + |
| 58 | + # Check for prime factors from 2 to sqrt(n) |
| 59 | + for factor in range(2, int(math.sqrt(num)) + 1): |
| 60 | + if num % factor == 0: |
| 61 | + # Increment prime score for each prime factor |
| 62 | + prime_scores[index] += 1 |
| 63 | + |
| 64 | + # Remove all occurrences of the prime factor from num |
| 65 | + while num % factor == 0: |
| 66 | + num //= factor |
| 67 | + |
| 68 | + # If num is still greater than or equal to 2, it's a prime factor |
| 69 | + if num >= 2: |
| 70 | + prime_scores[index] += 1 |
| 71 | + |
| 72 | + # Initialize next and previous dominant index arrays |
| 73 | + next_dominant = [n] * n |
| 74 | + prev_dominant = [-1] * n |
| 75 | + |
| 76 | + # Stack to store indices for monotonic decreasing prime score |
| 77 | + decreasing_prime_score_stack = [] |
| 78 | + |
| 79 | + # Calculate the next and previous dominant indices for each number |
| 80 | + for index in range(n): |
| 81 | + # While the stack is not empty and the current prime score is greater than the stack's top |
| 82 | + while ( |
| 83 | + decreasing_prime_score_stack |
| 84 | + and prime_scores[decreasing_prime_score_stack[-1]] |
| 85 | + < prime_scores[index] |
| 86 | + ): |
| 87 | + top_index = decreasing_prime_score_stack.pop() |
| 88 | + |
| 89 | + # Set the next dominant element for the popped index |
| 90 | + next_dominant[top_index] = index |
| 91 | + |
| 92 | + # If the stack is not empty, set the previous dominant element for the current index |
| 93 | + if decreasing_prime_score_stack: |
| 94 | + prev_dominant[index] = decreasing_prime_score_stack[-1] |
| 95 | + |
| 96 | + # Push the current index onto the stack |
| 97 | + decreasing_prime_score_stack.append(index) |
| 98 | + |
| 99 | + # Calculate the number of subarrays in which each element is dominant |
| 100 | + num_of_subarrays = [0] * n |
| 101 | + for index in range(n): |
| 102 | + num_of_subarrays[index] = (next_dominant[index] - index) * ( |
| 103 | + index - prev_dominant[index] |
| 104 | + ) |
| 105 | + |
| 106 | + # Priority queue to process elements in decreasing order of their value |
| 107 | + processing_queue = [] |
| 108 | + |
| 109 | + # Push each number and its index onto the priority queue |
| 110 | + for index in range(n): |
| 111 | + heapq.heappush(processing_queue, (-nums[index], index)) |
| 112 | + |
| 113 | + score = 1 |
| 114 | + |
| 115 | + # Helper function to compute the power of a number modulo MOD |
| 116 | + def _power(base, exponent): |
| 117 | + res = 1 |
| 118 | + |
| 119 | + # Calculate the exponentiation using binary exponentiation |
| 120 | + while exponent > 0: |
| 121 | + # If the exponent is odd, multiply the result by the base |
| 122 | + if exponent % 2 == 1: |
| 123 | + res = (res * base) % self.MOD |
| 124 | + |
| 125 | + # Square the base and halve the exponent |
| 126 | + base = (base * base) % self.MOD |
| 127 | + exponent //= 2 |
| 128 | + |
| 129 | + return res |
| 130 | + |
| 131 | + # Process elements while there are operations left |
| 132 | + while k > 0: |
| 133 | + # Get the element with the maximum value from the queue |
| 134 | + num, index = heapq.heappop(processing_queue) |
| 135 | + num = -num # Negate back to positive |
| 136 | + |
| 137 | + # Calculate the number of operations to apply on the current element |
| 138 | + operations = min(k, num_of_subarrays[index]) |
| 139 | + |
| 140 | + # Update the score by raising the element to the power of operations |
| 141 | + score = (score * _power(num, operations)) % self.MOD |
| 142 | + |
| 143 | + # Reduce the remaining operations count |
| 144 | + k -= operations |
| 145 | + |
| 146 | + return score |
| 147 | + |
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