136. Single Number🖖

README.md

@@ -22,6 +22,7 @@ continually updating 😃.
 * [88. Merge Sorted Array](src/0088_merge_sorted_array/msa.go)   *`sort;`*  *`array`*
 * [121. Best Time to Buy and Sell Stock](src/0121_best_time_to_buy_and_sell_stock/maxprofit.go)   *`dynamic programming;`*  *`array`*
 * [122. Best Time to Buy and Sell Stock II](src/0122_best_time_to_buy_and_sell_stock_2/maxprofit.go)   *`greedy;`*  *`array`*
+* [136. Single Number](src/0136_single_number/single_number.go)   *`hash table;`*  *`bit manipulation`*
 * [167. Two Sum II - Input array is sorted](src/0167_two_sum2/two_sum2.go)   *`double index;`*  *`binary search`*
 * [179. Largest Number](src/0179_largest_number/ln.go)   *`sort`*
 * [200. Number of Islands](src/0200_number_of_island/number_of_island.go)   *`dfs;`*  *`bfs`*

src/0136_single_number/single_number.go

@@ -0,0 +1,37 @@
+/*
+136. Single Number
+https://leetcode.com/problems/single-number/
+
+Given a non-empty array of integers, every element appears twice except for one. Find that single one.
+*/
+// time: 2019-02-01
+
+package sn
+
+// time complexity: O(n)
+// space complexity: O(n)
+func singleNumber(nums []int) int {
+	record := make(map[int]int)
+	for _, num := range nums {
+		if _, ok := record[num]; ok {
+			delete(record, num)
+		} else {
+			record[num] = 1
+		}
+	}
+	var res int
+	for key := range record {
+		res = key
+	}
+	return res
+}
+
+// time complexity: O(n)
+// space complexity: O(1)
+func singleNumber1(nums []int) int {
+	res := 0
+	for _, num := range nums {
+		res ^= num
+	}
+	return res
+}

src/0136_single_number/single_number_test.go

@@ -0,0 +1,22 @@
+package sn
+
+import "testing"
+
+func TestSingleNumber(t *testing.T) {
+	testCases := [][]int{
+		{2, 2, 1},
+		{4, 1, 2, 1, 2},
+	}
+	expected := []int{1, 4}
+	testFuncs := []func([]int) int{
+		singleNumber, singleNumber1,
+	}
+
+	for _, testFunc := range testFuncs {
+		for index, nums := range testCases {
+			if res := testFunc(nums); res != expected[index] {
+				t.Errorf("expected %d, got %d", expected[index], res)
+			}
+		}
+	}
+}

src/README.md

@@ -57,6 +57,7 @@
 |0121|[121. Best Time to Buy and Sell Stock](0121_best_time_to_buy_and_sell_stock/maxprofit.go)|Easy||
 |0122|[122. Best Time to Buy and Sell Stock II](0122_best_time_to_buy_and_sell_stock_2/maxprofit.go)|Easy|*`greedy`*|
 |0125|[Valid Palindrome](0125_valid_palindrome/valid_palindrome.go)|Easy||
+|0136|[136. Single Number](0136_single_number/single_number.go)|Easy|*`hash table;`* *`bit manipulation`*|
 |0144|[144. Binary Tree Preorder Traversal](0144_binary_tree_preorder_traversal/binary_tree_preorder_traversal.go)|Medium|*`binary tree`*|
 |0150|[150. Evaluate Reverse Polish Notation](0150_evaluate_reverse_polish_notation/evaluate_reverse_polish_notation.go)|Medium|*`stack`*|
 |0153|[153. Find Minimum in Rotated Sorted Array](0153_find_minimum_in_rotated_sorted_array/fmirsa.go)|Medium|*`binary search`*|