Add Find Longest Subarray Sum Is Less Or Equal K Problem (#16)

algorithms-and-data-structures/src/main/java/com/xtenzq/arrays/SlidingWindow.java

@@ -0,0 +1,26 @@
+package com.xtenzq.arrays;
+
+public class SlidingWindow {
+
+    /**
+     * Finds the length of the longest subarray with a sum less than or equal to a given value.
+     *
+     * @param nums the array of positive integers
+     * @param k the maximum allowed sum of the subarray
+     * @return the length of the longest subarray with a sum less than or equal to {@code k}
+     * @implNote This method runs in {@code O(n)} time complexity and {@code O(1)} space complexity,
+     * where {@code n} is the length of {@code nums}.
+     */
+    public static int findLongestSubArraySumLessOrEqualK(int[] nums, int k) {
+        int left = 0, answer = 0, curr = 0;
+        for (int right = 0; right < nums.length; right++) {
+            curr += nums[right];
+            while (curr > k) {
+                curr -= nums[left];
+                left++;
+            }
+            answer = Math.max(answer, right - left + 1);
+        }
+        return answer;
+    }
+}

algorithms-and-data-structures/src/test/java/com/xtenzq/arrays/SlidingWindowTest.java

@@ -0,0 +1,51 @@
+package com.xtenzq.arrays;
+
+import org.junit.jupiter.api.Test;
+
+import static com.xtenzq.arrays.SlidingWindow.findLongestSubArraySumLessOrEqualK;
+import static org.junit.jupiter.api.Assertions.*;
+
+class SlidingWindowTest {
+
+    @Test
+    void testFindLongestSubArraySumLessOrEqualK_Example() {
+        int[] nums = {3, 2, 1, 3, 1, 1};
+        int k = 5;
+        assertEquals(3, findLongestSubArraySumLessOrEqualK(nums, k));
+    }
+
+    @Test
+    void testFindLongestSubArraySumLessOrEqualK_AllElementsLessThanK() {
+        int[] nums = {1, 2, 1, 2, 1};
+        int k = 5;
+        assertEquals(3, findLongestSubArraySumLessOrEqualK(nums, k));
+    }
+
+    @Test
+    void testFindLongestSubArraySumLessOrEqualK_SingleElementEqualsK() {
+        int[] nums = {5};
+        int k = 5;
+        assertEquals(1, findLongestSubArraySumLessOrEqualK(nums, k));
+    }
+
+    @Test
+    void testFindLongestSubArraySumLessOrEqualK_SingleElementGreaterThanK() {
+        int[] nums = {6};
+        int k = 5;
+        assertEquals(0, findLongestSubArraySumLessOrEqualK(nums, k));
+    }
+
+    @Test
+    void testFindLongestSubArraySumLessOrEqualK_MultipleSubarrays() {
+        int[] nums = {1, 2, 3, 4, 5};
+        int k = 5;
+        assertEquals(2, findLongestSubArraySumLessOrEqualK(nums, k));
+    }
+
+    @Test
+    void testFindLongestSubArraySumLessOrEqualK_EmptyArray() {
+        int[] nums = {};
+        int k = 5;
+        assertEquals(0, findLongestSubArraySumLessOrEqualK(nums, k));
+    }
+}