Variant of Problem 370 -- Range Addition (O(n) python solution)
We just need to genearte the valid K range( 1 or 2 interval) for each position in the array. Then use the solution from Problem 370. L record the range need to 
We just need to genearte the valid K range( 1 or 2 interval) for each position in the array. Then use the solution from Problem 370. L record the range need to be added. I misunderstand the shift direction, so need to modify it afterwards.\n```\nL = []\nn = len(A)\nfor i in xrange(n):\n\tA[i] = i - A[i]\n\tif A[i]+(n-i-1)>=0:\n\t\t\tL.append([max(-A[i],0),n-i-1])\n\tif A[i]-1>=0:\n\t\t\tK = max(n - A[i], n - i)\n\t\t\tL.append([K,n-1])\n```
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