Leetcode Problem 2104. Sum of Subarray Ranges

2104. Sum of Subarray Ranges

Leetcode Solutions

Monotonic Stack Approach

  1. Initialize two variables minSum and maxSum to store the sum of minimum and maximum values of subarrays respectively.
  2. Use two separate monotonic stacks, one for finding the minimum values (minStack) and one for finding the maximum values (maxStack).
  3. Iterate through the array indices from 0 to n (inclusive) to calculate minSum and maxSum using the respective stacks.
  4. For each index i, pop elements from minStack while the top of the stack is greater than or equal to nums[i]. Calculate the contribution of these elements to minSum.
  5. Similarly, pop elements from maxStack while the top of the stack is less than or equal to nums[i]. Calculate the contribution of these elements to maxSum.
  6. After processing each element, push the current index i onto both stacks.
  7. After the loop, process the remaining elements in both stacks.
  8. The final answer is maxSum - minSum, which represents the sum of all subarray ranges.
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Brute Force Approach

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