finish "136. Single Number". Fix #136

Author: diguage

README.adoc

@@ -683,12 +683,12 @@
 //|{leetcode_base_url}/candy/[Candy]
 //|{source_base_url}/Candy.java[Java]
 //|Hard
-//
-//|136
-//|{leetcode_base_url}/single-number/[Single Number]
-//|{source_base_url}/SingleNumber.java[Java]
-//|Easy
-//
+
+|136
+|{leetcode_base_url}/single-number/[Single Number]
+|{source_base_url}/SingleNumber.java[Java]
+|Easy
+
 //|137
 //|{leetcode_base_url}/single-number-ii/[Single Number II]
 //|{source_base_url}/SingleNumberIi.java[Java]

src/main/java/com/diguage/algorithm/leetcode/SingleNumber.java

@@ -0,0 +1,60 @@
+package com.diguage.algorithm.leetcode;
+
+import java.util.Objects;
+
+/**
+ * = 136. Single Number
+ *
+ * https://leetcode.com/problems/single-number/[Single Number - LeetCode]
+ *
+ * Given a non-empty array of integers, every element appears twice except for one. Find that single one.
+ *
+ * *Note:*
+ *
+ * Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?
+ *
+ * .Example 1:
+ * [source]
+ * ----
+ * Input: [2,2,1]
+ * Output: 1
+ * ----
+ *
+ * .Example 2:
+ * [source]
+ * ----
+ * Input: [4,1,2,1,2]
+ * Output: 4
+ * ----
+ *
+ * @author D瓜哥, https://www.diguage.com/
+ * @since 2020-01-01 12:38
+ */
+public class SingleNumber {
+    /**
+     * Runtime: 0 ms, faster than 100.00% of Java online submissions for Single Number.
+     *
+     * Memory Usage: 38.5 MB, less than 98.52% of Java online submissions for Single Number.
+     */
+    public int singleNumber(int[] nums) {
+        if (Objects.isNull(nums) || nums.length == 0) {
+            return 0;
+        }
+        int result = nums[0];
+        for (int i = 1; i < nums.length; i++) {
+            result ^= nums[i];
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        SingleNumber solution = new SingleNumber();
+        int[] a1 = {2, 2, 1};
+        int r1 = solution.singleNumber(a1);
+        System.out.println((r1 == 1) + " : " + r1);
+
+        int[] a2 = {4, 1, 2, 1, 2};
+        int r2 = solution.singleNumber(a2);
+        System.out.println((r2 == 4) + " : " + r2);
+    }
+}