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Author: MukulParasar

0033-search-in-rotated-sorted-array/0033-search-in-rotated-sorted-array.java

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+class Solution {
+    public int search(int[] nums, int target) {
+        int pivot = findPivot(nums);
+        if (pivot == -1) {
+            // run normal binary search
+            return binarySearch(nums, target, 0, nums.length - 1);
+        }
+
+        // if pivot is found, two ascending sorted arrays found -> check if pivot is target. Otherwise, run binary search in each(separately)
+        if (nums[pivot] == target) {
+            return pivot;
+        }
+        if (target >= nums[0]) {
+            return binarySearch(nums, target, 0, pivot - 1);
+        } else {
+            return binarySearch(nums, target, pivot + 1, nums.length - 1);
+        }
+    }
+
+    int binarySearch(int[] arr, int target, int start, int end) {
+        while(start <= end) {
+            // find the middle element
+//            int mid = (start + end) / 2; // might be possible that (start + end) exceeds the range of int in java
+            int mid = start + (end - start) / 2;
+            if (target < arr[mid]) {
+                end = mid - 1;
+            } else if (target > arr[mid]) {
+                start = mid + 1;
+            } else {
+                // ans found
+                return mid;
+            }
+        }
+        return -1;
+    }
+
+    int findPivot(int[] arr) {
+        int start = 0;
+        int end = arr.length - 1;
+        while (start <= end) {
+            int mid = start + (end - start) / 2;
+            if (mid < end && arr[mid] > arr[mid + 1]) {
+                return mid;
+            }
+            if (mid > start && arr[mid - 1] > arr[mid]) {
+                return mid - 1;
+            }
+            if (arr[start] >= arr[mid]) {
+                end = mid - 1;
+            } else {
+                start = mid + 1;
+            }
+        }
+        return -1;
+    }
+}