Question

Implement a hash function that hashes pictures, where a picture is a 500 by 500 array of Pixels and a Pixel is a struct with three components r, g, b of type unsigned char.

unsigned int hash(Pixel pic[][500], unsigned int tableSize);

Hint: Convert each pixel to a nonnegative integer, then combine the 25,000 numbers to get a hash value.

Answer 1

Points to consider:

1. For the above function for testing, we are forming a random pic with r, g, b or unsigned.
2. Then we have to find the hash value, and for which we are using the sum % 256 as the hash function
3. The sum would be of all the r,g,b of each pixel.

Code

#include<iostream>
using namespace std;

struct Pixel
{
   unsigned char r, g, b;  
};
unsigned int hash(Pixel pic[][500])
{
   int hash = 0;
   for(int i = 0;i<500;i++)
   {
       for(int j = 0;j<500;j++)
       {
           Pixel cur = pic[i][j];
           hash += (unsigned int)cur.r + (unsigned int)cur.g + (unsigned int)cur.b;
           hash %= 256;
       }
   }
   return hash;
}
int main()
{
   Pixel pic[500][500];
   for(int i = 0;i<500;i++)
   {
       for(int j = 0; j < 500;j++)
       {
           Pixel cur;
           cur.r = (unsigned char)j;
           cur.g = (unsigned char)j;
           cur.b = (unsigned char)j;
           pic[i][j] = cur;
       }
      
   }
   cout<<"Hash Value of the above Pic is: "<<hash(pic)<<endl;
}

Code Snippet

1 2 #include<iostream> using namespace std; struct Pixel minn unsigned char r, g, b; 8_unsigned int hash(Pixel pic[](500]) int hash = 0; for(int i = 0;i<500; i++) for(int j = 0; j<500; j++) Pixel cur = pic[i][j]; hash += (unsigned int)cur.r + (unsigned int)cur.g + (unsigned int)cur.b; hash %= 256; return hash; int main() Pixel pic[500] [580]; for(int i = 0;i<500; i++) { for(int j = 0; j < 500;j++) Pixel cur; cur.r = (unsigned char)j; cur.g = (unsigned char)j; cur.b = (unsigned char)j; pic[i][j] = cur; cout<<"Hash Value of the above Pic is: "<<hash(pic)<<endl;

Sample Output:

- 0 X C:\Users\visha OneDrive\Documents\C++\hashFunction.exe Hash Value of the above Pic is: 8 Process exited after 4.388 seconds with return value o Press any key to continue ...

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