New Problem Solution - "1700. Number of Students Unable to Eat Lunch"

Author: haoel

Diff for: README.md

@@ -107,6 +107,7 @@ LeetCode
 |1716|[Calculate Money in Leetcode Bank](https://leetcode.com/problems/calculate-money-in-leetcode-bank/) | [C++](./algorithms/cpp/calculateMoneyInLeetcodeBank/CalculateMoneyInLeetcodeBank.cpp)|Easy|
 |1711|[Count Good Meals](https://leetcode.com/problems/count-good-meals/) | [C++](./algorithms/cpp/countGoodMeals/CountGoodMeals.cpp)|Medium|
 |1710|[Maximum Units on a Truck](https://leetcode.com/problems/maximum-units-on-a-truck/) | [C++](./algorithms/cpp/maximumUnitsOnATruck/MaximumUnitsOnATruck.cpp)|Easy|
+|1700|[Number of Students Unable to Eat Lunch](https://leetcode.com/problems/number-of-students-unable-to-eat-lunch/) | [C++](./algorithms/cpp/numberOfStudentsUnableToEatLunch/NumberOfStudentsUnableToEatLunch.cpp)|Easy|
 |1695|[Maximum Erasure Value](https://leetcode.com/problems/maximum-erasure-value/) | [C++](./algorithms/cpp/maximumErasureValue/MaximumErasureValue.cpp)|Medium|
 |1694|[Reformat Phone Number](https://leetcode.com/problems/reformat-phone-number/) | [C++](./algorithms/cpp/reformatPhoneNumber/ReformatPhoneNumber.cpp)|Easy|
 |1625|[Lexicographically Smallest String After Applying Operations](https://leetcode.com/problems/lexicographically-smallest-string-after-applying-operations/) | [C++](./algorithms/cpp/lexicographicallySmallestStringAfterApplyingOperations/LexicographicallySmallestStringAfterApplyingOperations.cpp)|Medium|

Diff for: algorithms/cpp/numberOfStudentsUnableToEatLunch/NumberOfStudentsUnableToEatLunch.cpp

@@ -0,0 +1,75 @@
+// Source : https://leetcode.com/problems/number-of-students-unable-to-eat-lunch/
+// Author : Hao Chen
+// Date   : 2021-05-10
+
+/***************************************************************************************************** 
+ *
+ * The school cafeteria offers circular and square sandwiches at lunch break, referred to by numbers 0 
+ * and 1 respectively. All students stand in a queue. Each student either prefers square or circular 
+ * sandwiches.
+ * 
+ * The number of sandwiches in the cafeteria is equal to the number of students. The sandwiches are 
+ * placed in a stack. At each step:
+ * 
+ * 	If the student at the front of the queue prefers the sandwich on the top of the stack, they 
+ * will take it and leave the queue.
+ * 	Otherwise, they will leave it and go to the queue's end.
+ * 
+ * This continues until none of the queue students want to take the top sandwich and are thus unable 
+ * to eat.
+ * 
+ * You are given two integer arrays students and sandwiches where sandwiches[i] is the type of the 
+ * ith sandwich in the stack (i = 0 is the top of the stack) and students[j] is the preference of 
+ * the jth student in the initial queue (j = 0 is the front of the queue). Return the number of 
+ * students that are unable to eat.
+ * 
+ * Example 1:
+ * 
+ * Input: students = [1,1,0,0], sandwiches = [0,1,0,1]
+ * Output: 0 
+ * Explanation:
+ * - Front student leaves the top sandwich and returns to the end of the line making students = 
+ * [1,0,0,1].
+ * - Front student leaves the top sandwich and returns to the end of the line making students = 
+ * [0,0,1,1].
+ * - Front student takes the top sandwich and leaves the line making students = [0,1,1] and sandwiches 
+ * = [1,0,1].
+ * - Front student leaves the top sandwich and returns to the end of the line making students = 
+ * [1,1,0].
+ * - Front student takes the top sandwich and leaves the line making students = [1,0] and sandwiches = 
+ * [0,1].
+ * - Front student leaves the top sandwich and returns to the end of the line making students = [0,1].
+ * - Front student takes the top sandwich and leaves the line making students = [1] and sandwiches = 
+ * [1].
+ * - Front student takes the top sandwich and leaves the line making students = [] and sandwiches = [].
+ * Hence all students are able to eat.
+ * 
+ * Example 2:
+ * 
+ * Input: students = [1,1,1,0,0,1], sandwiches = [1,0,0,0,1,1]
+ * Output: 3
+ * 
+ * Constraints:
+ * 
+ * 	1 <= students.length, sandwiches.length <= 100
+ * 	students.length == sandwiches.length
+ * 	sandwiches[i] is 0 or 1.
+ * 	students[i] is 0 or 1.
+ ******************************************************************************************************/
+
+class Solution {
+public:
+    int countStudents(vector<int>& students, vector<int>& sandwiches) {
+        int st[2] = {0};
+        for(auto s: students) {
+            st[s]++;
+        }
+        int cnt = 0;
+        for(auto& san : sandwiches){
+            if (st[san] == 0) break;
+            st[san]--;
+            cnt++;
+        }
+        return students.size() - cnt;
+    }
+};