# Virtual Boolean Array - Google Top Interview Questions

### Problem Statement :

```Implement a boolean array which implements the following methods:

BooleanArray() which initializes an array of size 2 ** 31 with all false values.

void setTrue(int i) which sets the value at index i to true.

void setFalse(int i) which sets the value at index i to false.

void setAllTrue() which sets the value at every index to true.

void setAllFalse() which sets the value at every index to false.

boolean getValue(int i) which returns the value at index i.

Constraints

0 ≤ n ≤ 100,000 where n is the number of method calls

Example 1

Input

methods = ["constructor", "getValue", "setAllTrue", "getValue", "setFalse", "getValue"]

arguments = [[], , [], , , ]`

Output

[None, False, None, True, None, False]

Explanation

a = BooleanArray()

a.getValue(9) == False

a.setAllTrue()

a.getValue(3) == True

a.setFalse(4)

a.getValue(4) == False

Example 2

Input

methods = ["constructor", "setTrue", "getValue", "setFalse", "getValue"]

arguments = [[], , , , ]`

Output

[None, None, True, None, False]

Explanation

a = BooleanArray()

a.setTrue(5)

a.getValue(5) == True

a.setFalse(5)

a.getValue(5) == False```

### Solution :

```                        ```Solution in C++ :

class BooleanArray {
public:
bool base = false;
set<int> diffs;

BooleanArray() {
base = false;
diffs.clear();
}

void setTrue(int i) {
if (base == false)
diffs.insert(i);
else
diffs.erase(i);
}

void setFalse(int i) {
if (base == true)
diffs.insert(i);
else
diffs.erase(i);
}

void setAllTrue() {
base = true;
diffs.clear();
}

void setAllFalse() {
base = false;
diffs.clear();
}

bool getValue(int i) {
return (base == true ? (diffs.count(i) > 0 ? false : true)
: (diffs.count(i) > 0 ? true : false));
}
};```
```

```                        ```Solution in Java :

import java.util.*;

class BooleanArray {
public Map<Integer, Boolean> map;
public boolean allTrue;

public BooleanArray() {
map = new HashMap<>();
}

public void setTrue(int i) {
map.put(i, true);
}

public void setFalse(int i) {
map.put(i, false);
}

public void setAllTrue() {
map.clear();
allTrue = true;
}

public void setAllFalse() {
map.clear();
allTrue = false;
}

public boolean getValue(int i) {
if (map.containsKey(i))
return map.get(i);
return allTrue;
}
}```
```

```                        ```Solution in Python :

class BooleanArray:
def __init__(self):
self.arr = {}
self.default = False

def setTrue(self, i):
self.arr[i] = True

def setFalse(self, i):
self.arr[i] = False

def setAllTrue(self):
self.arr = {}
self.default = True

def setAllFalse(self):
self.arr = {}
self.default = False

def getValue(self, i):
if i not in self.arr:
return self.default

return self.arr[i]

immortal
96

1 year ago
Even more compact memory footprint depending upon assignment.

class BooleanArray:
def __init__(self):
self.state = False
self.d = set()

def clear(self):
self.d = set()

def setTrue(self, i):
if not self.state:
elif i in self.d:
self.d.remove(i)

def setFalse(self, i):
if self.state:
elif i in self.d:
self.d.remove(i)

def setAllTrue(self):
self.clear()
self.state = True

def setAllFalse(self):
self.clear()
self.state = False

def getValue(self, i):
if i in self.d:
return not self.state
return self.state```
```

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