Binary Search 1

LC33.java

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+// Time Complexity : O(logN)
+// Space Complexity : O(1)
+
+
+// Your code here along with comments explaining your approach
+//Create pointers low and high and calculate mid
+//check if the left side is sorted or the right side at this point.
+//if the left side is sorted, check if the target value lies in that window. If not, move the low pointer to mid+1.
+// same for the right side
+// return the mid element if target is found
+// else return -1 if while loop exits without finding the target value.
+
+class Solution {
+    public int search(int[] nums, int target) {
+        //1
+        int low = 0;
+        int high = nums.length - 1;
+
+        //2
+        while(low <= high){
+            int mid = low + (high - low)/2;
+
+            //3
+            if(nums[mid] == target){
+                return mid;
+            } else if(nums[mid] >= nums[low]){
+                if(target >= nums[low] && target < nums[mid]){
+                    high = mid - 1;
+                } else {
+                    low = mid + 1;
+                }
+            } else{
+                if(target > nums[mid] && target <= nums[high]){
+                    low = mid + 1;
+                } else{
+                    high = mid - 1;
+                }
+            }
+        }
+        //4
+        return -1;
+    }
+}

LC702.java

@@ -0,0 +1,42 @@
+// Time Complexity : O(logN)
+// Space Complexity : O(1)
+
+
+
+// Your code here along with comments explaining your approach
+//Create pointers low, high and calculate mid
+//keep updating value of high until you get Integer.MAX_VALUE because that means you have hit array out of bound
+//create a separate function specifically for binary search and use it to return the value in the search method.
+
+
+class Solution {
+    public int search(ArrayReader reader, int target) {
+        int low = 0;
+        int high = 1;
+
+        while(reader.get(high) != Integer.MAX_VALUE){
+            high = high*2;
+        }
+
+        return binarySearch(reader, low, high, target);
+
+    }
+
+    private int binarySearch(ArrayReader reader, int low, int high, int target){
+        while(low <= high){
+            int mid = low + (high - low)/2;
+
+            if(reader.get(mid) == target){
+                return mid;
+            } 
+            else if(reader.get(mid) > target){
+                high = mid - 1;
+            } 
+            else{
+                low = mid + 1;
+            }
+
+        }
+        return -1;
+    }
+}