Prefix Sum

Prefix Sum

1588. Sum of All Odd Length Subarrays

• better solution is math

  def sumOddLengthSubarrays(arr):
    accum = 0 
    prefix_sum = [0]
      
    for num in arr:
        accum += num
        prefix_sum.append(accum)
          
    total = 0
      
    for l in range(1, len(arr) + 1):
        for r in range(l, len(arr) + 1):
            if (r - l + 1) % 2 == 1:
                total += prefix_sum[r] - prefix_sum[l - 1]
                  
    return total