max height ladder possible using binary search - O(logn)

Author: NirmalSilwal

CodingBlocks Training/Day14/maxHeightLadder3.java

@@ -0,0 +1,35 @@
+package Lecture14;
+
+public class maxHeightLadder3 {
+
+	public static void main(String[] args) {
+
+		int n = 20;
+		System.out.println(maxHeight(n)); // 5
+
+		System.out.println(maxHeight(21)); // 6
+		System.out.println(maxHeight(100)); // 13
+		System.out.println(maxHeight(1)); // 1
+		System.out.println(maxHeight(0)); // -1
+		System.out.println(maxHeight(6)); // 3
+		System.out.println(maxHeight(7)); // 3
+	}
+
+	public static int maxHeight(int n) {
+		if (n < 1) {
+			return -1;
+		}
+		int left = 0, right = n, ans = -1;
+		while (left <= right) {
+			int height = (left + right) / 2;
+			int blocksNeeded = height * (height + 1) / 2;
+			if (blocksNeeded > n) {
+				right = height - 1;
+			} else {
+				ans = height;
+				left = height + 1;
+			}
+		}
+		return ans;
+	}
+}