All Problems

Problem title

Difficulty

Avg time to solve

Print Leaf Nodes

Easy

33 mins

Right View

Moderate

35 mins

Matrix Is Symmetric

Easy

10 mins

Convert binary tree to mirror tree

Easy

15 mins

Minimum Number Of Taps To Water Garden

Hard

15 mins

Rearrange Alternatively

Easy

15 mins

Count derangements

Moderate

35 mins

Given a string, find the next smallest palindrome

Easy

12 mins

Buses

Moderate

15 mins

Min Cost To Buy N Items

Easy

10 mins

Problem

Submissions

16

Avg. time to solve

15 min

Success Rate

85%

Problem Statement

```
Can you solve the problem in O(N) time?
```

```
The first line contains a single integer T representing the number of test cases.
The first line of each test case will contain the integer N.
The second and the last line of each test case will contain N single space-separated integers representing the elements of the array “ranges”.
```

```
For each test case, print a single integer representing the value of the minimum number of taps needed to open by the gardener to fill the whole garden.
```

```
You do not need to print anything, it has already been taken care of. Just implement the given function.
```

```
1 <= T <= 10
1 <= N <= 10^4
0 <= ranges[i] <= 100
Time Limit: 1 sec
```

```
2
3
0 0 0 0
7
1 2 1 0 2 1 0 1
```

```
-1
3
```

```
In test case 1, the ranges of taps are as follows : [ [ 0, 0 ], [ 1, 1 ], [ 2, 2 ] ]. So in the worst case, if we open all the taps, then it’s impossible to fill the gaps i.e (0-1), (1,2), (2,3). So it’s impossible to fill the garden.
In test case 2, the ranges of taps are as follows : [ [ -1, 1 ],[ -1, 3 ],[ 1, 3 ],[ 3, 3 ],[ 2, 6 ],[ 4, 6 ],[ 6, 6 ],[ 6, 8 ] ]. To fill the garden i.e [ 0, 7 ] , the gardener needs to open a minimum of three taps i.e. tap 2: [ -1, 3 ] , tap 5: [ 2, 6 ], tap 8: [ 6, 8 ] to fill the whole garden.
```

```
2
8
4 0 0 0 0 0 0 0 4
8
4 0 0 0 4 0 0 0 4
```

```
2
1
```

Java (SE 1.8)

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