New Problem Solution - "Count Items Matching a Rule"

Author: haoel

README.md

@@ -15,6 +15,7 @@ LeetCode
 |1781|[Sum of Beauty of All Substrings](https://leetcode.com/problems/sum-of-beauty-of-all-substrings/) | [C++](./algorithms/cpp/sumOfBeautyOfAllSubstrings/SumOfBeautyOfAllSubstrings.cpp)|Medium|
 |1780|[Check if Number is a Sum of Powers of Three](https://leetcode.com/problems/check-if-number-is-a-sum-of-powers-of-three/) | [C++](./algorithms/cpp/checkIfNumberIsASumOfPowersOfThree/CheckIfNumberIsASumOfPowersOfThree.cpp)|Medium|
 |1779|[Find Nearest Point That Has the Same X or Y Coordinate](https://leetcode.com/problems/find-nearest-point-that-has-the-same-x-or-y-coordinate/) | [C++](./algorithms/cpp/findNearestPointThatHasTheSameXOrYCoordinate/FindNearestPointThatHasTheSameXOrYCoordinate.cpp)|Easy|
+|1773|[Count Items Matching a Rule](https://leetcode.com/problems/count-items-matching-a-rule/) | [C++](./algorithms/cpp/countItemsMatchingARule/CountItemsMatchingARule.cpp)|Easy|
 |1763|[Longest Nice Substring](https://leetcode.com/problems/longest-nice-substring/) | [C++](./algorithms/cpp/longestNiceSubstring/LongestNiceSubstring.cpp)|Easy|
 |1761|[Minimum Degree of a Connected Trio in a Graph](https://leetcode.com/problems/minimum-degree-of-a-connected-trio-in-a-graph/) | [C++](./algorithms/cpp/minimumDegreeOfAConnectedTrioInAGraph/MinimumDegreeOfAConnectedTrioInAGraph.cpp)|Hard|
 |1760|[Minimum Limit of Balls in a Bag](https://leetcode.com/problems/minimum-limit-of-balls-in-a-bag/) | [C++](./algorithms/cpp/minimumLimitOfBallsInABag/MinimumLimitOfBallsInABag.cpp)|Medium|

algorithms/cpp/countItemsMatchingARule/CountItemsMatchingARule.cpp

@@ -0,0 +1,60 @@
+// Source : https://leetcode.com/problems/count-items-matching-a-rule/
+// Author : Hao Chen
+// Date   : 2021-03-14
+
+/***************************************************************************************************** 
+ *
+ * You are given an array items, where each items[i] = [typei, colori, namei] describes the type, 
+ * color, and name of the ith item. You are also given a rule represented by two strings, ruleKey and 
+ * ruleValue.
+ * 
+ * The ith item is said to match the rule if one of the following is true:
+ * 
+ * 	ruleKey == "type" and ruleValue == typei.
+ * 	ruleKey == "color" and ruleValue == colori.
+ * 	ruleKey == "name" and ruleValue == namei.
+ * 
+ * Return the number of items that match the given rule.
+ * 
+ * Example 1:
+ * 
+ * Input: items = [["phone","blue","pixel"],["computer","silver","lenovo"],["phone","gold","iphone"]], 
+ * ruleKey = "color", ruleValue = "silver"
+ * Output: 1
+ * Explanation: There is only one item matching the given rule, which is 
+ * ["computer","silver","lenovo"].
+ * 
+ * Example 2:
+ * 
+ * Input: items = [["phone","blue","pixel"],["computer","silver","phone"],["phone","gold","iphone"]], 
+ * ruleKey = "type", ruleValue = "phone"
+ * Output: 2
+ * Explanation: There are only two items matching the given rule, which are ["phone","blue","pixel"] 
+ * and ["phone","gold","iphone"]. Note that the item ["computer","silver","phone"] does not match.
+ * 
+ * Constraints:
+ * 
+ * 	1 <= items.length <= 104
+ * 	1 <= typei.length, colori.length, namei.length, ruleValue.length <= 10
+ * 	ruleKey is equal to either "type", "color", or "name".
+ * 	All strings consist only of lowercase letters.
+ ******************************************************************************************************/
+
+class Solution {
+public:
+    int countMatches(vector<vector<string>>& items, string ruleKey, string ruleValue) {
+        int idx;
+        switch(ruleKey[0]) {
+            case 't': idx = 0; break;
+            case 'c': idx = 1; break;
+            case 'n': idx = 2; break;
+            default: return 0;
+        }
+        
+        int cnt = 0;
+        for (auto& item : items) {
+            if (item[idx] == ruleValue) cnt++;
+        }
+        return cnt;
+    }
+};