CountItemsMatchingARule.cpp

// 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;
    }
};