Merge pull request #1696 from akgmage/dev

Dev

Author: akgmage

Binary Search/first_true.java

@@ -0,0 +1,41 @@
+/*
+    An array of boolean values is divided into two sections; the left section consists of all false and the 
+    right section consists of all true. Find the First True in a Sorted Boolean Array of the 
+    right section, i.e. the index of the first true element. If there is no true element, return -1.
+    
+    Input: arr = [false, false, true, true, true]
+    Output: 2
+
+    Explanation: first true's index is 2.
+*/
+public import java.util.Arrays;
+import java.util.List;
+import java.util.Scanner;
+import java.util.stream.Collectors;
+
+class Solution {
+    public static int findBoundary(List<Boolean> arr) {
+        int low = 0;                // Initialize the low pointer to the beginning of the list.
+        int high = arr.size() - 1;  // Initialize the high pointer to the end of the list.
+        int bv = -1;                // Initialize bv (boundary value) to -1.
+
+        while (low <= high) {
+            int mid = low + (high - low) / 2;  // Calculate the middle index.
+
+            if (arr.get(mid) == false) {
+                // If the element at the middle index is 'false',
+                // it means that the last 'true' value should be on the right side.
+                low = mid + 1;  // Move the low pointer to the right of mid.
+            } else {
+                // If the element at the middle index is 'true',
+                // update bv to the current middle index and continue searching on the left side.
+                bv = mid;       // Update bv to the current middle index.
+                high = mid - 1; // Move the high pointer to the left of mid.
+            }
+        }
+
+        // The loop ends when low > high, indicating that the search is complete.
+        // bv contains the index of the last 'true' value encountered.
+        return bv;
+    }
+}