Add solution #2023

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,692 LeetCode solutions in JavaScript
+# 1,693 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1551,6 +1551,7 @@
 2018|[Check if Word Can Be Placed In Crossword](./solutions/2018-check-if-word-can-be-placed-in-crossword.js)|Medium|
 2019|[The Score of Students Solving Math Expression](./solutions/2019-the-score-of-students-solving-math-expression.js)|Hard|
 2022|[Convert 1D Array Into 2D Array](./solutions/2022-convert-1d-array-into-2d-array.js)|Easy|
+2023|[Number of Pairs of Strings With Concatenation Equal to Target](./solutions/2023-number-of-pairs-of-strings-with-concatenation-equal-to-target.js)|Medium|
 2027|[Minimum Moves to Convert String](./solutions/2027-minimum-moves-to-convert-string.js)|Easy|
 2033|[Minimum Operations to Make a Uni-Value Grid](./solutions/2033-minimum-operations-to-make-a-uni-value-grid.js)|Medium|
 2037|[Minimum Number of Moves to Seat Everyone](./solutions/2037-minimum-number-of-moves-to-seat-everyone.js)|Easy|

solutions/2023-number-of-pairs-of-strings-with-concatenation-equal-to-target.js

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+/**
+ * 2023. Number of Pairs of Strings With Concatenation Equal to Target
+ * https://leetcode.com/problems/number-of-pairs-of-strings-with-concatenation-equal-to-target/
+ * Difficulty: Medium
+ *
+ * Given an array of digit strings nums and a digit string target, return the number of pairs of
+ * indices (i, j) (where i != j) such that the concatenation of nums[i] + nums[j] equals target.
+ */
+
+/**
+ * @param {string[]} nums
+ * @param {string} target
+ * @return {number}
+ */
+var numOfPairs = function(nums, target) {
+  const map = new Map();
+  let result = 0;
+
+  for (const num of nums) {
+    if (target.startsWith(num)) {
+      const suffix = target.slice(num.length);
+      result += map.get(suffix) || 0;
+    }
+    if (target.endsWith(num)) {
+      const prefix = target.slice(0, target.length - num.length);
+      result += map.get(prefix) || 0;
+    }
+    map.set(num, (map.get(num) || 0) + 1);
+  }
+
+  return result;
+};