153. Find Minimum in Rotated Sorted Array (#49)

* 153 solved.

* add 153 question link

Author: zwfang

README.md

@@ -103,6 +103,7 @@ continually updating 😃.
 * [34. Find First and Last Position of Element in Sorted Array](./src/0034_find_first_and_last_position_of_element_in_sorted_array/find_first_and_last_position_of_element_in_sorted_array.go)   *`array;`*  *`binary search`*
 * [35. Search Insert Position](src/0035_search_insert_position/search_insert_position.go)   *`array;`*  *`binary search`*
 * [69. Sqrt(x)](./src/0069_sqrtx/sqrtx.go)   *`math;`*  *`binary search`*
+* [153. Find Minimum in Rotated Sorted Array](src/0153_find_minimum_in_rotated_sorted_array/fmirsa.go)
 * [704. Binary Search](./src/0704_binary_search/binary_search.go)
 
 ### Math

src/0153_find_minimum_in_rotated_sorted_array/fmirsa.go

@@ -0,0 +1,35 @@
+/*
+153. Find Minimum in Rotated Sorted Array
+https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/
+
+Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.
+
+(i.e.,  [0,1,2,4,5,6,7] might become  [4,5,6,7,0,1,2]).
+
+Find the minimum element.
+
+You may assume no duplicate exists in the array.
+*/
+// time: 2019-01-07
+
+package fmirsa
+
+// binary search
+// time complexity: O( log n)
+// space complexity: O(1)
+func findMin(nums []int) int {
+	var (
+		low  int
+		high = len(nums) - 1
+		mid  int
+	)
+	for low < high {
+		mid = low + (high-low)>>1
+		if nums[high] < nums[mid] {
+			low = mid + 1
+		} else {
+			high = mid
+		}
+	}
+	return nums[low]
+}

src/0153_find_minimum_in_rotated_sorted_array/fmirsa_test.go

@@ -0,0 +1,11 @@
+package fmirsa
+
+import "testing"
+
+func TestFindMin(t *testing.T) {
+	nums := []int{3, 4, 5, 1, 2}
+	expected := 1
+	if res := findMin(nums); res != expected {
+		t.Errorf("expected %d, got %d", expected, res)
+	}
+}

src/README.md

@@ -59,6 +59,7 @@
 |0125|[Valid Palindrome](0125_valid_palindrome/valid_palindrome.go)|Easy||
 |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`*|
 |0167|[Two Sum II - Input array is sorted](./0167_two_sum2/two_sum2.go)|Easy|*`对撞指针(双索引)`*|
 |0198|[House Robber](./0198_house_robber/house_robber.go)|Easy|*`memory search;`* *`dynamic programming`*|
 |0209|[Minimum Size Subarray Sum](./0209_minimum_size_subarray_sum/minimum_size_subarray_sum.go)|Medium|*`sliding window`*|