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authorJack Sangdahl <jack@pngu.org>2024-12-27 19:04:58 -0700
committerJack Sangdahl <jack@pngu.org>2024-12-27 19:04:58 -0700
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parenta52ccc2d81430bae1862eebf40055815e1ff1c73 (diff)
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689. maximum sum of 3 non-overlapping subarrays
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+# 689. Maximum Sum of 3 Non-Overlapping Subarrays
+
+"""
+given an integer array 'nums' and an integer 'k', find three non-overlapping
+subarrays of length 'k' with maximum sum and return them. return the result
+as a list of indices representing the starting position of each interval
+(0-indexed). if there are multiple answers, return the lexicographcially
+smallest one
+"""
+
+
+class Solution(object):
+ def max_sumOfThreeSubarrays(self, nums, k):
+ """
+ :type nums: List[int]
+ :type k: int
+ :rtype: List[int]
+ """
+ n = len(nums)
+ max_sum = 0
+ sum = [0]
+ left = [0] * n
+ right = [n - k] * n
+ ans = [0, 0, 0]
+ for i in nums:
+ sum.append(sum[-1] + i)
+ tot = sum[k] - sum[0]
+ for i in range(k, n):
+ if sum[i + 1] - sum[i + 1 - k] > tot:
+ left[i] = i + 1 - k
+ tot = sum[i + 1] - sum[i + 1 - k]
+ else:
+ left[i] = left[i - 1]
+ tot = sum[n] - sum[n - k]
+ for i in range(n - k - 1, -1, -1):
+ if sum[i + k] - sum[i] > tot:
+ right[i] = i
+ tot = sum[i + k] - sum[i]
+ else:
+ right[i] = right[i + 1]
+ for i in range(k, n - 2 * k + 1):
+ l, r = left[i - 1], right[i + k]
+ tot = (sum[i + k] - sum[i]) + (sum[l + k] - sum[l]) + (sum[r + k] - sum[r])
+ if tot > max_sum:
+ max_sum = tot
+ ans = [l, i, r]
+ return ans
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ print(obj.max_sumOfThreeSubarrays(nums=[1, 2, 1, 2, 6, 7, 5, 1], k=2))
+ print(obj.max_sumOfThreeSubarrays(nums=[1, 2, 1, 2, 1, 2, 1, 2, 1], k=2))