add skeleton for 751

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_751.java

@@ -0,0 +1,59 @@
+package com.fishercoder.solutions;
+
+import java.util.List;
+
+/**
+ * 751. IP to CIDR
+ *
+ * Given a start IP address ip and a number of ips we need to cover n,
+ * return a representation of the range as a list (of smallest possible length) of CIDR blocks.
+ * A CIDR block is a string consisting of an IP, followed by a slash, and then the prefix length.
+ * For example: "123.45.67.89/20". That prefix length "20" represents the number of common prefix bits in the specified range.
+ *
+ * Example 1:
+ * Input: ip = "255.0.0.7", n = 10
+ * Output: ["255.0.0.7/32","255.0.0.8/29","255.0.0.16/32"]
+ * Explanation:
+ * The initial ip address, when converted to binary, looks like this (spaces added for clarity):
+ * 255.0.0.7 -> 11111111 00000000 00000000 00000111
+ *
+ * The address "255.0.0.7/32" specifies all addresses with a common prefix of 32 bits to the given address,
+ * ie. just this one address.
+ *
+ * The address "255.0.0.8/29" specifies all addresses with a common prefix of 29 bits to the given address:
+ * 255.0.0.8 -> 11111111 00000000 00000000 00001000
+ * Addresses with common prefix of 29 bits are:
+ * 11111111 00000000 00000000 00001000
+ * 11111111 00000000 00000000 00001001
+ * 11111111 00000000 00000000 00001010
+ * 11111111 00000000 00000000 00001011
+ * 11111111 00000000 00000000 00001100
+ * 11111111 00000000 00000000 00001101
+ * 11111111 00000000 00000000 00001110
+ * 11111111 00000000 00000000 00001111
+ *
+ * The address "255.0.0.16/32" specifies all addresses with a common prefix of 32 bits to the given address,
+ * ie. just 11111111 00000000 00000000 00010000.
+ *
+ * In total, the answer specifies the range of 10 ips starting with the address 255.0.0.7 .
+ *
+ * There were other representations, such as:
+ * ["255.0.0.7/32","255.0.0.8/30", "255.0.0.12/30", "255.0.0.16/32"],
+ * but our answer was the shortest possible.
+ *
+ * Also note that a representation beginning with say, "255.0.0.7/30" would be incorrect,
+ * because it includes addresses like 255.0.0.4 = 11111111 00000000 00000000 00000100
+ * that are outside the specified range.
+ * Note:
+ * ip will be a valid IPv4 address.
+ * Every implied address ip + x (for x < n) will be a valid IPv4 address.
+ * n will be an integer in the range [1, 1000].
+ * */
+public class _751 {
+    public static class Solution1 {
+        public List<String> ipToCIDR(String ip, int n) {
+            //TODO: implement it
+            return null;
+        }
+    }
+}