Solution of Binary Search - 1

SearchIn2DMatrix

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+// This solution we discussed in class.
+// Time complexity o(log m * n)
+// Space complexity o(1)
+
+class Solution {
+    public boolean searchMatrix(int[][] matrix, int target) {
+     int m = matrix.length;
+     int n = matrix[0].length;
+     int low = 0, high = m*n-1;
+
+     while(low<=high) {
+        int mid = low + (high - low) /2;
+        int row = mid / n , col = mid % n;
+
+        if(matrix[row][col] == target) return true;
+        else if(matrix[row][col] < target) {
+                low = mid + 1;
+        } else {
+                high = mid - 1;
+        }
+     }
+     return false;
+
+    }
+}

SearchInRotatedArray

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+//Time complexity o(log n)
+//Space complexity o(1)
+
+class Solution {
+    public int search(int[] nums, int target) {
+        int low = 0 , high = nums.length - 1;
+
+        while(low<=high) {
+            int mid = low + (high - low) /2;
+            if(nums[mid] == target) return mid;
+            else if(nums[low] <= nums[mid]) {
+                if(nums[low] <= target && target <= nums[mid]) {
+                    high = mid - 1;
+                } else {
+                    low = mid + 1;
+                }
+            } else {
+                if(nums[mid] < target && target <= nums[high]) {
+                    low = mid + 1;
+                } else {
+                    high = mid - 1;
+                }
+            }
+        }
+        return -1;
+    }
+}

SearchInSortedUnknownArray

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+/**
+ * // This is ArrayReader's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * interface ArrayReader {
+ *     public int get(int index) {}
+ * }
+ */
+
+// Time Complexity o(log n) if there are n number of elements in unknown array.
+// Space complexity o(1)
+
+class Solution {
+    public int search(ArrayReader reader, int target) {
+        int low = 0 , high = 1;
+        while(reader.get(high) < target) {
+            low = high;
+            high = 2*high;
+        }
+
+        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;
+
+    }
+}