feat(slidingwindow): add SmallestSubarrayWithSum algorithm

Author: nihalsingh373

src/main/java/com/thealgorithms/slidingwindow/SmallestSubarrayWithSum.java

@@ -0,0 +1,54 @@
+package com.thealgorithms.slidingwindow;
+
+/**
+ * The Sliding Window algorithm is used to find the length of the smallest
+ * contiguous subarray whose sum is greater than or equal to a given target.
+ *
+ * <p>Time Complexity: O(n)
+ * <br>Space Complexity: O(1)
+ *
+ * <p>This class provides a static method to find the minimum length subarray
+ * that satisfies the given sum condition.
+ *
+ * <p>Example:
+ * <pre>
+ * int[] nums = {2, 3, 1, 2, 4, 3};
+ * int target = 7;
+ * int result = SmallestSubarrayWithSum.findMinSubArrayLen(target, nums);
+ * System.out.println(result); // Output: 2 (subarray [4,3])
+ * </pre>
+ *
+ * @author Nihal
+ */
+public final class SmallestSubarrayWithSum {
+
+    // Prevent instantiation
+    private SmallestSubarrayWithSum() {
+    }
+
+    /**
+     * Finds the minimal length of a contiguous subarray of which the sum ≥ target.
+     *
+     * @param target the target sum
+     * @param nums the array of positive integers
+     * @return the length of the smallest subarray with sum ≥ target,
+     *         or 0 if no such subarray exists
+     */
+    public static int findMinSubArrayLen(int target, int[] nums) {
+        int windowStart = 0;
+        int windowSum = 0;
+        int minLength = Integer.MAX_VALUE;
+
+        for (int windowEnd = 0; windowEnd < nums.length; windowEnd++) {
+            windowSum += nums[windowEnd];
+
+            while (windowSum >= target) {
+                minLength = Math.min(minLength, windowEnd - windowStart + 1);
+                windowSum -= nums[windowStart];
+                windowStart++;
+            }
+        }
+
+        return (minLength == Integer.MAX_VALUE) ? 0 : minLength;
+    }
+}