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    "https://leetcode.com/problems/check-if-n-and-its-double-exist\n",
    "\n",
    "\n",
    "\n",
    "Runtime: 1 ms, faster than 98.26% of Java online submissions for Check If N and Its Double Exist.\n",
    "Memory Usage: 38.1 MB, less than 99.39% of Java online submissions for Check If N and Its Double Exist.\n",
    "\n",
    "\n",
    "\n",
    "```java\n",
    "class ContainsResult {\n",
    "    boolean contains;\n",
    "    int index;\n",
    "\n",
    "    ContainsResult(boolean contains, int index) {\n",
    "        this.contains = contains;\n",
    "        this.index = index;\n",
    "    }\n",
    "}\n",
    "\n",
    "class Solution {\n",
    "    public boolean checkIfExist(int[] arr) {\n",
    "        for (int i=0; i<arr.length; ++i) {\n",
    "            int v = arr[i];\n",
    "            int d_v = v * 2;\n",
    "            ContainsResult result = this.contains(d_v, arr);\n",
    "            if (result.contains && result.index != i) {\n",
    "                return true;\n",
    "            }\n",
    "        }\n",
    "        return false;\n",
    "    }\n",
    "\n",
    "    private ContainsResult contains(int v, int[] arr) {\n",
    "        for (int i=0; i < arr.length; ++i) {\n",
    "            if (arr[i] == v) {\n",
    "                return new ContainsResult(true, i);\n",
    "            }\n",
    "        }\n",
    "        return new ContainsResult(false, 0);\n",
    "    }\n",
    "\n",
    "    public static void main(String[] args) {\n",
    "        int[] nums = { 10,2,5,3 };\n",
    "        // int[] nums = { 2, 1, 3 };\n",
    "        boolean r = new Solution().checkIfExist(nums);\n",
    "        System.out.println(r);\n",
    "    }\n",
    "}\n",
    "```"
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