Complete Binary-Search-2

Find_First_and_last_element_of_Array.cpp

@@ -0,0 +1,58 @@
+// for this particular problem we can perfrom the binary search for finding the first element 
+// and we if find the first element we compare it with its previous element if it is not the 
+// first index we can perfrom continue the binary search on left half
+// once we have frist index we can perfrom the binary search on the right half starting from first index
+// if we find the target we compare it with its next index if it is not the target we got our last index
+
+
+class Solution {
+    int BinarySearchFirst(int start, int end, int target,vector<int>& nums)
+    {
+        while(start<=end)
+        {
+            int mid = start + (end- start)/2;
+            if(nums[mid]==target)
+            {
+                if(mid == 0 || nums[mid-1]!=target)
+                    return mid;
+                else
+                    end = mid -1;
+            }
+            else if( target<=nums[mid])
+                end = mid -1;
+            else 
+                start = mid +1;
+        }
+        return -1;
+    }
+    int BinarySearchSecond(int start, int end, int target,vector<int>& nums)
+    {
+        while(start<=end)
+        {
+            int mid = start + (end- start)/2;
+            if(nums[mid]==target)
+            {
+                if(mid == end ||nums[mid+1]!=target)
+                    return mid;
+                else
+                    start = mid +1;
+            }
+            else if(target <= nums[mid])
+                end = mid -1;
+            else 
+                start = mid +1;
+        }
+        return -1;
+    }
+public:
+    vector<int> searchRange(vector<int>& nums, int target) {
+        if(nums.size() == 0) return {-1,-1};
+        int first = BinarySearchFirst(0, nums.size()-1,target,nums);
+        if(first == -1)
+            return {-1,-1};
+        int second = BinarySearchSecond(first,nums.size()-1,target,nums);
+        if(second == -1)
+            return {first ,first};
+        return{first,second};
+    }   
+};

Find_peak_element.cpp

@@ -0,0 +1,19 @@
+class Solution {
+public:
+    int findPeakElement(vector<int>& nums) {
+        int start = 0;
+        int end = nums.size()-1;
+
+        while(start <= end)
+        {
+            int mid = start + (end-start)/2;
+            if((mid == 0 || nums[mid] > nums[mid-1]) && (mid == nums.size()-1||nums[mid] > nums[mid+1]))
+                return mid;
+            else if(mid > 0 && nums[mid-1] > nums[mid])
+                end = mid-1;
+            else
+                start = mid+1;
+        }
+     return -1;
+    }
+};

find_the_minimum_rotated_sorted_array.cpp

@@ -0,0 +1,27 @@
+class Solution {
+public:
+    int findMin(vector<int>& nums) {
+        int start = 0;
+        int end = nums.size() -1;
+        //base case
+        if(nums.size()==1)
+            return nums[0];
+        if(nums[start] < nums[end])
+            return nums[start];
+
+        while(start <= end)
+        {
+            int mid = start + (end-start)/2;
+            if(nums[mid] > nums[mid +1])
+                return nums[mid+1];
+            if(nums[mid- 1] > nums[mid] )
+                return nums[mid];
+            else if (nums[mid] > nums[start])
+                start = mid +1;
+            else
+                end = mid -1;
+        }
+        return -1;
+    }
+};
+