Completed BinarySearch-2 Problems

2024_Problem10_Find_Minimum_in_Rotated_Array.java

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+//153. Find Min in Rotated Array - https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/description/
+//Time Complexity: O(n)
+//Space Complexity: O(1)
+
+class Solution {
+    public int findMin(int[] nums) {
+
+        int low = 0, high = nums.length-1;
+
+        while(low<=high){
+            //if we are in sorted part of the array
+            if(nums[low] < nums[high])
+                return nums[low];
+            //calculate mid
+            int mid = low + (high-low)/2;
+            //check if mid is the minimum
+            if((mid == low || nums[mid] < nums[mid-1]) &&
+                    (mid == high || nums[mid] < nums[mid+1])){
+                return nums[mid];
+            }
+            //sorted side - move to unsorted part
+            else if(nums[low] <= nums[mid]){ //Right sorted
+                low = mid+1;
+            }else {
+                high=mid-1; //left sorted
+            }
+        }
+        return -1;
+    }
+}

2024_Problem11_Find_peak_Element.java

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+//162. Find Peak Element - https://leetcode.com/problems/find-peak-element/description/
+//Time Complexity: log(n)
+//Space Complexity: O(1)
+
+class Solution {
+    public int findPeakElement(int[] nums) {
+
+        int low = 0, high = nums.length-1;
+        while(low <= high){
+            int mid = low + (high-low)/2;
+            if((mid == low || nums[mid-1] < nums[mid]) &&
+                    (mid == high || nums[mid+1] < nums[mid])){
+                return mid;
+            }
+            //moving to the greater side
+            else if(nums[mid] < nums[mid+1]){
+                low = mid + 1;
+            }
+            //moving to the greater side
+            else if(nums[mid] > nums[mid+1]){
+                high = mid - 1;
+            }
+        }
+        return -1;
+    }
+}

2024_Problem9_Find_First_and_Last_Position_of_Element_in_Sorted_Array.java

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+//34. Find First and Last position of an Element in Sorted Array - https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/
+//Time Complexity: O(2log(n)) ~ log(n)
+//Space Complexity: O(1)
+
+class Solution {
+
+    //to get first index
+    public int binarySearchLeft(int[] nums, int target) {
+        int low = 0; int high = nums.length - 1;
+        while(low <= high){
+            int mid = low + (high - low)/2;
+            if(nums[mid] == target){
+                if(mid == 0 || nums[mid] > nums[mid-1]){
+                    return mid;
+                } else {
+                    high = mid-1;
+                }
+            } else if(nums[mid] > target){
+                high = mid-1;
+            } else {
+                low = mid+1;
+            }
+        }
+        return -1;
+    }
+
+    //to get last index
+    public int binarySearchRight(int[] nums, int target) {
+        int low = 0; int high = nums.length - 1;
+        while(low <= high){
+            int mid = low + (high - low)/2;
+            if(nums[mid] == target){
+                if(mid == nums.length -1 || nums[mid] < nums[mid+1]){
+                    return mid;
+                } else {
+                    low = mid+1;
+                }
+            } else if(nums[mid] > target){
+                high = mid-1;
+            } else {
+                low = mid+1;
+            }
+        }
+        return -1;
+    }
+
+    public int[] searchRange(int[] nums, int target) {
+        //base case
+        if(nums == null || nums.length == 0){
+            return new int[]{-1,-1};
+        }
+        int first = binarySearchLeft(nums, target);
+        int last = binarySearchRight(nums, target);
+        return new int[]{first, last};
+    }
+}