Number of strictly increasing Buildings from right with distinct Colors

Given an integer and two integer arrays H[] and C[] of size where H[] stores the height of consecutive buildings and C[] stores the color codes for those building in which they are painted.

The task is to determine how many colors are visible at once from the view on the right i.e. right of the rightmost building.

Examples:

Input: K = 5, H[] = {5, 4, 3, 2, 3}, C[] = {1, 2, 3, 4, 5}
Output: 3 Input: K = 5, H[] = {1, 2, 3, 4, 5}, C[] = {3, 3, 3, 3, 3}
Output: 1

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Appraoch: On observing carefully, the above problem can be simplified to find the number of strictly increasing buildings from right with distinct colors.

1. Store the Last element of Height array in max variable.
2. Now in an array Arr, at position corresponding to the element at the last of the colour array store 1.
3. Now start traversing the Height array from n-2 to 0.
4. If we get element greater than max then store that variable in max and again in array Arr, at position correspond to the ith element in the colour array store 1.
5. At last Count the number of 1’s present in the array Arr. It gives the total number of colour visible from the end.

Below is the implementation of the above approach:

C++

 // C++ implementation of above approach    #include using namespace std;    // Function to return the number of // colors visible int colourVisible(int height[], int colour[], int K) {     int arr[K + 1] = { 0 }, visible = 0;        int max = height[K - 1];     arr[colour[K - 1]] = 1;        for (int i = K - 2; i >= 0; i--) {         if (height[i] > max) {             max = height[i];             arr[colour[i]] = 1;         }     }        // Count the Number of 1's     for (int i = 1; i <= K; i++) {         if (arr[i] == 1)             visible++;     }        return visible; }    // Driver code int main() {     int height[] = { 3, 5, 1, 2, 3 };     int colour[] = { 1, 2, 3, 4, 3 };     int K = sizeof(colour) / sizeof(colour);        cout << colourVisible(height, colour, K);        return 0; }

Java

 //Java  implementation of above approach     import java.io.*;    class GFG {     // Function to return the number of  // colors visible  static int colourVisible(int height[], int colour[], int K)  {      int arr[]=new int[K + 1] ;     int visible = 0;         int max = height[K - 1];      arr[colour[K - 1]] = 1;         for (int i = K - 2; i >= 0; i--) {          if (height[i] > max) {              max = height[i];              arr[colour[i]] = 1;          }      }         // Count the Number of 1's      for (int i = 1; i <= K; i++) {          if (arr[i] == 1)              visible++;      }         return visible;  }     // Driver code             public static void main (String[] args) {            int height[] = { 3, 5, 1, 2, 3 };      int colour[] = { 1, 2, 3, 4, 3 };      int K = colour.length;         System.out.println (colourVisible(height, colour, K));     } }

Python3

 # Python3 implementation of above approach    # Function to return the number of # colors visible def colourVisible(height, colour, K):     arr = [0 for i in range(K + 1)]     visible = 0        max = height[K - 1]     arr[colour[K - 1]] = 1            i = K - 2     while(i >= 0):         if (height[i] > max):             max = height[i]             arr[colour[i]] = 1         i -= 1            # Count the Number of 1 complement     for i in range(1, K + 1, 1):             if (arr[i] == 1):                 visible += 1            return visible    # Driver code if __name__ == '__main__':     height = [3, 5, 1, 2, 3]      colour = [1, 2, 3, 4, 3]      K = len(colour)        print(colourVisible(height, colour, K))    # This code is contributed by # Surendra_Gangwar

C#

 // C# implementation of above approach using System;    class GFG { // Function to return the number of  // colors visible  static int colourVisible(int []height,                           int []colour, int K)  {      int []arr=new int[K + 1] ;      int visible = 0;         int max = height[K - 1];      arr[colour[K - 1]] = 1;         for (int i = K - 2; i >= 0; i--)      {          if (height[i] > max)          {              max = height[i];              arr[colour[i]] = 1;          }      }         // Count the Number of 1's      for (int i = 1; i <= K; i++)     {          if (arr[i] == 1)              visible++;      }         return visible;  }     // Driver code  static public void Main () {     int []height = { 3, 5, 1, 2, 3 };      int []colour = { 1, 2, 3, 4, 3 };      int K = colour.Length;             Console.WriteLine(colourVisible(height, colour, K));  } }    // This code is contributed by Sach_Code

PHP

 = 0; \$i--)     {         if (\$height[\$i] > \$max)         {             \$max = \$height[\$i];             \$arr[\$colour[\$i]] = 1;         }     }        // Count the Number of 1's     for (\$i = 1; \$i <= \$K; \$i++)     {         if (\$arr[\$i] == 1)             \$visible++;     }        return \$visible; }    // Driver code \$height = array( 3, 5, 1, 2, 3 ); \$colour = array( 1, 2, 3, 4, 3 ); \$K = count(\$colour);    echo colourVisible(\$height, \$colour, \$K);    // This code is contributed by mits ?>

Output:

2

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