cs: add «2429. Minimize XOR»

URL:	https://leetcode.com/problems/minimize-xor/
Signed-off-by: Matej Focko <me@mfocko.xyz>

cs/minimize-xor.cs

@@ -0,0 +1,36 @@
+public class Solution {
+    private int MostSignificantBit(int num) {
+        var mostSignificant = 0;
+        for (var mask = 1; mask <= num; mask <<= 1) {
+            if ((num & mask) != 0) {
+                mostSignificant = mask;
+            }
+        }
+        return mostSignificant;
+    }
+
+    public int MinimizeXor(int num1, int num2) {
+        var bitCount = int.PopCount(num2);
+        var mask = MostSignificantBit(num1);
+
+        var minimal = 0;
+
+        // Cancel out upper bits
+        for (; mask > 0 && bitCount > 0; mask >>= 1) {
+            if ((num1 & mask) != 0) {
+                minimal |= mask;
+                --bitCount;
+            }
+        }
+
+        // Add remaining bits from the “bottom”
+        for (mask = 1; bitCount > 0; mask <<= 1) {
+            if ((minimal & mask) == 0) {
+                minimal |= mask;
+                --bitCount;
+            }
+        }
+
+        return minimal;
+    }
+}