Binary-Search-2

Minimum in Rotated Sorted Array.py

@@ -0,0 +1,16 @@
+class Solution:
+    def findMin(self, nums: List[int]) -> int:
+        low = 0
+        high = len(nums)-1
+
+        while low<=high:
+            if nums[low]<=nums[high]:
+                return nums[low]
+            mid = low + (high-low)//2
+            if (nums[mid]<=nums[mid-1]) and (nums[mid]<=nums[mid+1]):
+                return nums[mid]
+            elif nums[low]<=nums[mid]:
+                low = mid+1
+            else:
+                high = mid-1
+

README.md

@@ -19,6 +19,45 @@ Example 2:
 Input: nums = [5,7,7,8,8,10], target = 6
 Output: [-1,-1]
 
+class Solution:
+
+    def searchRange(self, nums: List[int], target: int) -> List[int]:
+        if len(nums)==0:
+            return [-1,-1]
+        start = self.start_index(nums,target)
+        last = self.last_index(nums,target,start)
+        return [start,last]
+
+    def start_index(self, nums, target):
+        low = 0
+        high = len(nums)-1
+        ind = -1
+        while low<=high:
+            mid = low+(high-low)//2
+            if nums[mid]==target:
+                ind = mid
+                high = mid-1
+            elif nums[mid]>=target:
+                high = mid-1
+            elif nums[mid]<=target:
+                low = mid+1
+        return ind
+
+    def last_index(self, nums, target,start):
+        low = start
+        high = len(nums)-1
+        ind = -1
+        while low<=high:
+            mid = low+(high-low)//2
+            if nums[mid]==target:
+                ind = mid
+                low = mid+1
+            elif nums[mid]>=target:
+                high = mid-1
+            elif nums[mid]<=target:
+                low = mid+1
+        return ind
+
 ## Problem 2: (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.
@@ -37,6 +76,26 @@ Example 2:
 Input: [4,5,6,7,0,1,2]
 Output: 0
 
+Time complexity: O(logn)
+
+class Solution:
+
+    def findMin(self, nums: List[int]) -> int:
+        low = 0
+        high = len(nums)-1
+        if len(nums)==0:
+            return -1
+        while low<=high:
+            if nums[low]<nums[high]:
+                return nums[low]
+            mid = low+(high-low)//2
+            if (mid==0 or nums[mid]<nums[mid-1]) and (mid==len(nums)-1 or nums[mid]<nums[mid+1]):
+                return nums[mid]
+            elif nums[low]<=nums[mid]:
+                low = mid+1
+            else:
+                high = mid-1
+
 ## Problem 3: (https://leetcode.com/problems/find-peak-element/)
 A peak element is an element that is greater than its neighbors.
 
@@ -56,10 +115,25 @@ Example 2:
 Input: nums = [1,2,1,3,5,6,4]
 Output: 1 or 5 
 Explanation: Your function can return either index number 1 where the peak element is 2, 
-
              or index number 5 where the peak element is 6.
 Note:
 
 Your solution should be in logarithmic complexity.
 
+class Solution:
+
+    def findPeakElement(self, nums: List[int]) -> int:
+        low = 0
+        high = len(nums)-1
+        if len(nums)==0:
+            return -1
+        while low<=high:
+            mid = low + (high-low)//2
+            if ((mid==0 or nums[mid-1]<nums[mid]) and (mid==len(nums)-1 or nums[mid]>nums[mid+1])):
+                return mid
+            elif (mid!=len(nums)-1 and nums[mid+1]>nums[mid]):
+                low = mid+1
+            else:
+                high = mid-1
+
 

findPeakElement.py

@@ -0,0 +1,14 @@
+class Solution:
+    def findPeakElement(self, nums: List[int]) -> int:
+        low = 0
+        high = len(nums)-1
+
+        while low<high: 
+            mid = low + (high-low)//2 
+            if (mid==0 or nums[mid]>nums[mid-1]) and (mid==len(nums)-1 or nums[mid]>nums[mid+1]): 
+                return  mid 
+            elif (nums[mid]<nums[mid+1]): 
+                low = mid+1  
+            else:
+                high = mid 
+        return low

searchRange.py

@@ -0,0 +1,44 @@
+class Solution:
+    def SearchFirst(self, nums, target, low, high):
+
+        while low<=high:
+            mid = low + (high-low)//2
+            if nums[mid]==target:
+                if (mid==low or nums[mid-1]<nums[mid]):
+                    return mid
+                else:
+                    high = mid-1
+            elif nums[mid]<target:
+                low = mid+1
+            else:
+                high = mid-1
+        return -1
+
+    def SearchLast(self, nums, target, low, high):
+
+        while low<=high:
+            mid = low + (high-low)//2
+            if nums[mid]==target:
+                if (mid==len(nums)-1 or nums[mid+1]>nums[mid]):
+                    return mid
+                else:
+                    low = mid+1
+            elif nums[mid]<target:
+                low = mid+1
+            else:
+                high = mid-1
+        return -1
+
+    def searchRange(self, nums: List[int], target: int) -> List[int]:
+        low = 0
+        high = len(nums)-1
+
+        if len(nums)==0 or target<nums[low] or target>nums[high]:
+            return [-1,-1]
+
+        firstIndex = self.SearchFirst(nums, target, low, high)
+        if firstIndex == -1:
+            return [-1,-1]
+        LastIndex = self.SearchLast(nums, target, firstIndex, high)
+        return [firstIndex,LastIndex] 
+