Distinct pairs done

Author: rampatra

src/main/java/com/leetcode/math/ExcelSheetColumnNumber.java

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+package com.leetcode.math;
+
+/**
+ * Level: Easy
+ * Problem Link: https://leetcode.com/problems/excel-sheet-column-number/
+ * Problem Description:
+ * Given a column title as appear in an Excel sheet, return its corresponding column number.
+ *
+ * For example:
+ *
+ *  A -> 1
+ *  B -> 2
+ *  C -> 3
+ *  ...
+ *  Z -> 26
+ *  AA -> 27
+ *  AB -> 28
+ *  ...
+ *
+ * Example 1:
+ * Input: "A"
+ * Output: 1
+ *
+ * Example 2:
+ * Input: "AB"
+ * Output: 28
+ *
+ * Example 3:
+ * Input: "ZY"
+ * Output: 701
+ *
+ * @author rampatra
+ * @since 2019-05-31
+ */
+public class ExcelSheetColumnNumber {
+
+    private static int titleToNumber(String title) {
+        return 0;
+    }
+
+    public static void main(String[] args) {
+
+    }
+}

src/main/java/com/rampatra/arrays/DistinctPairs.java

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+package com.rampatra.arrays;
+
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Level: Easy
+ * Problem Description:
+ * Given an array and a target sum, return the number of distinct pairs whose sum is equal to the target sum.
+ * <p>
+ * For Example, given an array [1, 2, 3, 6, 7, 8, 9, 1] and a target sum of 10,
+ * the 7 pairs, i.e, (1, 9), (2, 8), (3, 7), (8, 2), (9, 1), (9, 1), and (1, 9) all sum to 10 but there are only
+ * three distinct pairs, i.e, (1, 9), (2, 8), and (3, 7) so the answer would be 3.
+ *
+ * @author rampatra
+ * @since 2019-06-03
+ */
+public class DistinctPairs {
+
+    /**
+     * Time complexity: O(n), n = size of the array
+     * Space complexity: O(n)
+     *
+     * @param arr
+     * @param targetSum
+     * @return
+     */
+    private static int numberOfDistinctPairs(int[] arr, int targetSum) {
+        Set<Integer> numSet = new HashSet<>();
+        Set<Set<Integer>> pairSet = new HashSet<>();
+
+        for (int i = 0; i < arr.length; i++) {
+            if (numSet.contains(targetSum - arr[i])) {
+                Set<Integer> pair = new HashSet<>();
+                pair.add(arr[i]);
+                pair.add(targetSum - arr[i]);
+                pairSet.add(pair);
+            }
+            numSet.add(arr[i]);
+        }
+
+        return pairSet.size();
+    }
+
+    public static void main(String[] args) {
+        System.out.println(numberOfDistinctPairs(new int[]{1, 2, 3, 6, 7, 8, 9, 1}, 1));
+        System.out.println(numberOfDistinctPairs(new int[]{1, 2, 3, 6, 7, 8, 9, 1}, 2));
+        System.out.println(numberOfDistinctPairs(new int[]{1, 2, 3, 6, 7, 8, 9, 1}, 10));
+    }
+}