Code Nation interview questions

There is a one-dimensional garden of length 'N'. On each of the positions from 0 to 'N', there is a fountain, and this fountain’s water can reach up to a certain range as explained further. In other words, there are 'N' + 1 fountains located at positions 0, 1, 2, 3, …. 'N' which can be activated in the garden. You are given an integer 'N' and an array/list 'ARR' of length 'N' + 1, where each index of the array denotes the coverage limit of a particular fountain. A fountain at index 'i' can water the area ranging from the position 'i' - 'ARR'['i'] to 'i' + 'ARR'['i']. Your task is to find the minimum number of fountains that have to be activated such that the whole garden from position 0 to 'N' has access to the water from at least some fountain. Note: 1. 0-based indexing is used in the array. 2. We only care about the garden from 0 to 'N' only. So if i - 'ARR'['i'] < 0 or i + 'ARR'['i'] > 'N', you may ignore the exceeding area. 3. If some fountain covers the garden from position 'A' to position 'B', it means that the water from this fountain will spread to the whole line segment with endpoints 'A' and 'B'. Input Format: The first line of the input contains an integer 'T', denoting the number of test cases. The first line of each test case contains the integer 'N', denoting the size of the garden. The second line of each test case contains 'N' + 1 space-separated integers denoting the array elements. Output Format: For each test case, print a single integer that corresponds to the minimum number of fountains to be activated.