add rearranging fruits

greedy_methods/rearranging_fruits.py

@@ -0,0 +1,61 @@
+from collections import defaultdict
+
+
+def min_cost(basket1: list[int], basket2: list[int]) -> int:
+    """
+    Compute the minimum cost to make two baskets identical by swapping fruits.
+
+    Each fruit is represented by an integer value. The goal is to make both baskets
+    have the same multiset of elements with the minimum swap cost. Each swap cost
+    is defined as the minimum of the swapped fruit's value and twice the smallest
+    fruit value in both baskets.
+
+    If it's impossible to make the baskets identical, return -1.
+
+    Args:
+        basket1 (list[int]): The first basket of fruits.
+        basket2 (list[int]): The second basket of fruits.
+
+    Returns:
+        int: The minimum total cost, or -1 if impossible.
+
+    Examples:
+        >>> min_cost([4, 2, 2, 2], [1, 4, 1, 2])
+        1
+        >>> min_cost([1, 2, 3, 4], [2, 3, 4, 1])
+        0
+        >>> min_cost([1, 1, 1, 1], [1, 1, 1, 1])
+        0
+        >>> min_cost([1, 2, 2], [2, 1, 1])
+        -1
+        >>> min_cost([5, 3, 3, 2], [2, 5, 5, 3])
+        -1
+    """
+    n = len(basket1)
+    freq: defaultdict[int, int] = defaultdict(int)
+    mn: float = float("inf")
+
+    for i in range(n):
+        freq[basket1[i]] += 1
+        freq[basket2[i]] -= 1
+        mn = min(mn, basket1[i], basket2[i])
+
+    to_swap: list[int] = []
+    for j, k in freq.items():
+        if k % 2 != 0:
+            return -1
+        to_swap += [j] * (abs(k) // 2)
+
+    to_swap.sort()
+    res: int = 0
+    for i in range(len(to_swap) // 2):
+        res += min(to_swap[i], 2 * int(mn))
+
+    return res
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+    print("All doctests passed.")