Create 2001-number-of-pairs-of-interchangeable-rectangles.c

Create the C solution as the same solution in the YouTube video "https://www.youtube.com/watch?v=lEQ8ZlLOuyQ"

Author: MHamiid

c/2001-number-of-pairs-of-interchangeable-rectangles.c

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+typedef struct hash_entry {
+    double* ratio;            /* we'll use this field as the key */
+    long long count;
+    UT_hash_handle hh;      /* makes this structure hashable */
+} hash_entry;
+
+long long interchangeableRectangles(int** rectangles, int rectanglesSize, int* rectanglesColSize){
+    hash_entry* ratioCountMap = NULL;
+    long long res = 0;
+
+    for(size_t i = 0; i < rectanglesSize; i++)
+    {
+        // Calculate the ratio (W / H)
+        double* ratio = (double*)malloc(sizeof(double));
+        *ratio = (double)rectangles[i][0] / rectangles[i][1];
+
+        hash_entry* retrievedMapEntry;
+        HASH_FIND_PTR(ratioCountMap, ratio, retrievedMapEntry);
+
+        // If the ratio already exists in the map then increment its count
+        if(retrievedMapEntry)
+        {
+            // Free the allocated memory for the ratio
+            free(ratio);
+            retrievedMapEntry->count += 1;
+        }
+        else
+        {
+            // If the ratio doesn't exist in the map then create a new map entry for it and add it to the map
+            hash_entry* mapEntryToAdd = (hash_entry*)malloc(sizeof(hash_entry)); 
+            mapEntryToAdd->ratio = ratio;
+            mapEntryToAdd->count = 1; 
+            HASH_ADD_KEYPTR(hh, ratioCountMap, mapEntryToAdd->ratio, sizeof(double), mapEntryToAdd);
+        }
+    }
+
+    for (hash_entry* retrievedMapEntry = ratioCountMap; retrievedMapEntry != NULL; retrievedMapEntry = retrievedMapEntry->hh.next)
+    {
+        res += (retrievedMapEntry->count * (retrievedMapEntry->count - 1)) / 2;
+    }
+
+    return res;
+}