Filling Bookcase Shelves.js

// Runtime: 92 ms (Top 69.01%) | Memory: 42.4 MB (Top 98.59%)
var minHeightShelves = function(books, shelfWidth) {
    let booksArr = []

    for(let i = 0; i < books.length; i++) {
        let remainingWidth = shelfWidth - books[i][0]
        let bookHeight = books[i][1]

        let maxHeight = bookHeight

        let prevSum = booksArr[i - 1] !== undefined ? booksArr[i - 1] : 0
        let minSumHeight = bookHeight + prevSum

        for(let x = i - 1; x >= 0 ; x--) {

            let prevBookWidth = books[x][0]
            let prevBookHeight = books[x][1]
            if(remainingWidth - prevBookWidth < 0) break
            remainingWidth -= prevBookWidth

            prevSum = booksArr[x - 1] !== undefined ? booksArr[x - 1] : 0

            maxHeight = Math.max(maxHeight, prevBookHeight)

            minSumHeight = Math.min(prevSum + maxHeight, minSumHeight)
        }
        booksArr[i] = minSumHeight
    }

    return booksArr[books.length - 1]
};