Add SB Curated (copied from the smartbugs repository).

dataset/denial_of_service/dos_number.sol

@@ -0,0 +1,47 @@
+/*
+ * @source: https://github.com/SmartContractSecurity/SWC-registry/blob/master/test_cases/dos_gas_limit/dos_number.sol
+ * @author: -
+ * @vulnerable_at_lines: 18,19,20,21,22
+ */
+
+pragma solidity ^0.4.25;
+
+contract DosNumber {
+
+    uint numElements = 0;
+    uint[] array;
+
+    function insertNnumbers(uint value,uint numbers) public {
+
+        // Gas DOS if number > 382 more or less, it depends on actual gas limit
+        // <yes> <report> DENIAL_OF_SERVICE
+        for(uint i=0;i<numbers;i++) {
+            if(numElements == array.length) {
+                array.length += 1;
+            }
+            array[numElements++] = value;
+        }
+    }
+
+    function clear() public {
+        require(numElements>1500);
+        numElements = 0;
+    }
+
+    // Gas DOS clear
+    function clearDOS() public {
+
+        // number depends on actual gas limit
+        require(numElements>1500);
+        array = new uint[](0);
+        numElements = 0;
+    }
+
+    function getLengthArray() public view returns(uint) {
+        return numElements;
+    }
+
+    function getRealLengthArray() public view returns(uint) {
+        return array.length;
+    }
+}