Add solution #1349

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,248 LeetCode solutions in JavaScript
+# 1,249 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1025,6 +1025,7 @@
 1346|[Check If N and Its Double Exist](./solutions/1346-check-if-n-and-its-double-exist.js)|Easy|
 1347|[Minimum Number of Steps to Make Two Strings Anagram](./solutions/1347-minimum-number-of-steps-to-make-two-strings-anagram.js)|Medium|
 1348|[Tweet Counts Per Frequency](./solutions/1348-tweet-counts-per-frequency.js)|Medium|
+1349|[Maximum Students Taking Exam](./solutions/1349-maximum-students-taking-exam.js)|Hard|
 1351|[Count Negative Numbers in a Sorted Matrix](./solutions/1351-count-negative-numbers-in-a-sorted-matrix.js)|Easy|
 1352|[Product of the Last K Numbers](./solutions/1352-product-of-the-last-k-numbers.js)|Medium|
 1356|[Sort Integers by The Number of 1 Bits](./solutions/1356-sort-integers-by-the-number-of-1-bits.js)|Easy|

solutions/1349-maximum-students-taking-exam.js

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+/**
+ * 1349. Maximum Students Taking Exam
+ * https://leetcode.com/problems/maximum-students-taking-exam/
+ * Difficulty: Hard
+ *
+ * Given a m * n matrix seats  that represent seats distributions in a classroom. If a seat is
+ * broken, it is denoted by '#' character otherwise it is denoted by a '.' character.
+ *
+ * Students can see the answers of those sitting next to the left, right, upper left and upper
+ * right, but he cannot see the answers of the student sitting directly in front or behind him.
+ * Return the maximum number of students that can take the exam together without any cheating
+ * being possible.
+ *
+ * Students must be placed in seats in good condition.
+ */
+
+/**
+ * @param {character[][]} seats
+ * @return {number}
+ */
+var maxStudents = function(seats) {
+  const rows = seats.length;
+  const cols = seats[0].length;
+  const cache = new Map();
+
+  return countStudents(0, 0);
+
+  function isValid(row, currMask, prevMask) {
+    for (let j = 0; j < cols; j++) {
+      if (!(currMask & (1 << j))) continue;
+      if (seats[row][j] === '#') return false;
+      if (j > 0 && (currMask & (1 << (j - 1)))) return false;
+      if (j < cols - 1 && (currMask & (1 << (j + 1)))) return false;
+      if (row > 0) {
+        if (j > 0 && (prevMask & (1 << (j - 1)))) return false;
+        if (j < cols - 1 && (prevMask & (1 << (j + 1)))) return false;
+      }
+    }
+    return true;
+  }
+
+  function countStudents(row, prevMask) {
+    if (row === rows) return 0;
+    const key = `${row},${prevMask}`;
+    if (cache.has(key)) return cache.get(key);
+
+    let maxCount = 0;
+    for (let currMask = 0; currMask < (1 << cols); currMask++) {
+      if (!isValid(row, currMask, prevMask)) continue;
+      const students = (currMask.toString(2).match(/1/g) || []).length;
+      maxCount = Math.max(maxCount, students + countStudents(row + 1, currMask));
+    }
+
+    cache.set(key, maxCount);
+    return maxCount;
+  }
+};