Added binary search

Author: Prashant Jain

src/in/knowledgegate/dsa/binarysearch/algos/BinarySearch.java

@@ -0,0 +1,25 @@
+package in.knowledgegate.dsa.binarysearch.algos;
+
+/**
+ * implement Binary Search on sorted array
+ * Example:
+ * sortedArr: -8, -5, 0, 3, 7, 11, 15
+ * Number to find: 7
+ * Number to find: 1
+ */
+public class BinarySearch {
+  public int search(int[] sortedArr, int target) {
+    int beg = 0, end = sortedArr.length - 1;
+    while (beg <= end) {
+      int mid = beg + (end - beg) / 2;
+      if (target == sortedArr[mid]) {
+        return mid;
+      } else if (target < sortedArr[mid]) {
+        end = mid - 1;
+      } else {
+        beg = mid + 1;
+      }
+    }
+    return -1;
+  }
+}

src/in/knowledgegate/dsa/binarysearch/problems/SquareRoot.java

@@ -0,0 +1,46 @@
+package in.knowledgegate.dsa.binarysearch.problems;
+
+/**
+ * Given a non-negative integer x, compute and
+ * return the square root of x.
+ *
+ * Since the return type is an integer, the
+ * decimal digits are truncated, and only the
+ * integer part of the result is returned.
+ *
+ * Note: You are not allowed to use any built-in
+ * exponent function or operator, such as
+ * pow(x, 0.5) or x ** 0.5.
+ *
+ * Example 1:
+ * Input: x = 4
+ * Output: 2
+ *
+ * Example 2:
+ * Input: x = 8
+ * Output: 2
+ * Explanation: The square root of 8 is 2.82842...,
+ * and since the decimal part is truncated,
+ * 2 is returned.
+ *
+ *
+ * Constraints:
+ * 0 <= x <= 231 - 1
+ */
+public class SquareRoot {
+  public int mySqrt(int x) {
+    int beg = 0, end = x;
+    while (beg <= end) {
+      int mid = beg + (end - beg) / 2;
+      long square = ((long)mid) * mid;
+      if (square == x) {
+        return mid;
+      } else if (square > x) {
+        end = mid - 1;
+      } else {
+        beg = mid + 1;
+      }
+    }
+    return end;
+  }
+}