feat: [arrays] Add 2pointers sliding window

* [strings] Format 2pointers sliding window code.

Author: manid2

cpp/arrays/2pointers-sliding-window-01.cpp

@@ -0,0 +1,66 @@
+/**
+ * Two pointers - sliding window technique - 01
+ * ============================================
+ *
+ * This technique is used to find subarrays or substrings given a set of
+ * conditions.
+ *
+ * Refer:
+ *
+ * https://www.geeksforgeeks.org/window-sliding-technique/
+ * https://discuss.leetcode.com/topic/30941/here-is-a-10-line-template-that-can-solve-most-substring-problems
+ */
+
+#include "tests.h"
+
+/* ===========================================================================
+ * Algorithms implementation
+ * ===========================================================================
+ */
+
+/* TC : O(n)
+ * SC : O(1)
+ */
+#define _2p_sw_maxSumKConseq_desc                                            \
+	"Two Pointers - Sliding Window - "                                   \
+	"Maximum sum of K consequent elements"
+
+int maxSumKConseq(const vi_t &a, int k)
+{
+	int n = size(a);
+	int r = 0, c = 0;
+	fii (i, k) r += a[i];
+	c = r;
+	for (int i = k; i < n; i++) {
+		c += a[i] - a[i - k];
+		r = max(r, c);
+	}
+	return r;
+}
+
+/* ===========================================================================
+ * Test code
+ * ===========================================================================
+ */
+#define _2p_sw_maxSumKConseq_check(i, k, e)                                  \
+	{                                                                    \
+		int a = maxSumKConseq(i, k);                                 \
+		CHECK_EQ(e, a);                                              \
+		string im = format("array = {}, k = {}", to_string(i), k);   \
+		SET_CUSTOM_SUCCESS_MSG(im, to_string(a));                    \
+		SHOW_OUTPUT(i, a);                                           \
+	}
+
+TEST(maxSumKConseq, _2p_sw_maxSumKConseq_desc)
+{
+	vi2_t _a{
+	    {100, 200, 300, 400},
+	    {1, 4, 2, 10, 23, 3, 1, 0, 20},
+	};
+	vi_t _k{2, 4};
+	vi_t _e{700, 39};
+	int n = size(_a);
+	fii (i, n) _2p_sw_maxSumKConseq_check(_a[i], _k[i], _e[i]);
+}
+
+INIT_TEST_MAIN();

cpp/strings/2pointers-sliding-window-01.cpp

@@ -2,6 +2,9 @@
  * Two pointers - sliding window technique - 01
  * ============================================
  *
+ * Two pointers - sliding window technique is used to find subarrays or
+ * substrings.
+ *
  * Refer:
  *
  * https://www.geeksforgeeks.org/window-sliding-technique/
@@ -19,17 +22,20 @@
  * SC : O(1)
  */
 
-#define _2p_sw_maxSubstrUniqChars_desc "Two Pointers - Sliding Window - "    \
-        "Longest Substring Without Repeating Characters"
+#define _2p_sw_maxSubstrUniqChars_desc                                       \
+	"Two Pointers - Sliding Window - "                                   \
+	"Longest Substring Without Repeating Characters"
 
 int maxSubstrUniqChars(const string &s)
 {
 	int n = size(s);
 	int l = 0, r = 0, d = 0;
 	vi_v(m, 128, 0);
 	while (l < n && r < n) {
-		if (!m[s[r]]++) r++, d = max(d, r - l);
-		else m[s[l++]] = 0;
+		if (!m[s[r]]++)
+			r++, d = max(d, r - l);
+		else
+			m[s[l++]] = 0;
 	}
 	return d;
 }