Rainwater trapping answer

#1

the output of the given test case should be 7 as the first elevation has height 0 and the water can also be collected there till height 2.

#2

@ppsingh12 can u please share the test case that u are talking about

#3

@ppsingh12 I am guessing that u are talking about this test case
10
0 2 1 3 0 1 2 1 2 1

a) when will water collect at index i?
water will collect at index i only when there exist some elevation higher then elevation of index i to its left as well as to its right.

now coming to your doubt.
if u see index 0 then u will find that there is not any elevation to its left and thus no water will be collected over index 0 elevation
i hope you find this helpful.

#4

@ppsingh12 hey pritpal if your doubt is resolved then please mark it resolved

#5

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#6

1

#7

refer this