Create 1349-maximum-students-taking-exam.js

Author: everthis

1349-maximum-students-taking-exam.js

@@ -0,0 +1,45 @@
+/**
+ * @param {character[][]} seats
+ * @return {number}
+ */
+const maxStudents = function (seats) {
+  if (!seats.length) return 0
+  const lastPos = 1 << seats[0].length
+  const classroom = seats.map((row) =>
+    row.reduce((a, c, i) => (c === '#' ? a : a | (1 << i)), 0)
+  )
+  const dp = new Array(seats.length + 1).fill(null).map(() => new Map())
+  dp[0].set(0, 0)
+  for (let row = 0; row < seats.length; row++) {
+    let queue = [0]
+    let numStudents = 0
+    while (queue.length > 0) {
+      const next = []
+      for (let arrangement of queue) {
+        let max = 0
+        for (let [prevArrang, count] of dp[row]) {
+          if (conflicts(prevArrang, arrangement)) continue
+          max = Math.max(max, count + numStudents)
+        }
+        dp[row + 1].set(arrangement, max)
+        for (let i = 1; i < lastPos; i <<= 1) {
+          if (canSit(classroom[row], arrangement, i)) next.push(arrangement | i)
+        }
+      }
+      queue = next
+      numStudents++
+    }
+  }
+  return Math.max(...dp[seats.length].values())
+}
+function conflicts(prev, curr) {
+  return prev & (curr << 1) || prev & (curr >> 1)
+}
+function canSit(row, arrangement, newStudent) {
+  return (
+    row & newStudent &&
+    !(arrangement & newStudent) &&
+    !(arrangement & (newStudent << 1)) &&
+    !(arrangement & (newStudent >> 1))
+  )
+}