72 lines
2.8 KiB
JavaScript
72 lines
2.8 KiB
JavaScript
// this is really slow but it works after a few seconds. I only learnt about memoising yesterday and couldn't get it to work. I will probably leave this as it is anyway.
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const fs = require('fs');
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const data = fs.readFileSync('input.txt', 'utf-8');
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// convert seat layout to matrix of bools
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let layoutMat = data.split('\n').map(l=>l.split('').map(s=>s=='L'));
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function iterate (stateMat, layoutMat){
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let nextState = stateMat.map(r => r.slice());
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for (let y = 0; y < layoutMat.length; y++) {
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for (let x = 0; x < layoutMat[1].length; x++) {
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if (!layoutMat[y][x]) continue // if this point is the floor, skip
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// count how many adjacent seats are full
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let seenSeats = lookAround(stateMat, x, y)
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// update seat according to rules in the challenge
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nextState[y][x] = stateMat[y][x] ? seenSeats < 5 : seenSeats == 0;
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// console.log('from', x,y,'i see', seenSeats, 'full chairs', nextState[y][x] ? 'so i sit here':'so i leave')
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}
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}
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return nextState
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}
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// look every direction from given co-ords
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function lookAround (stateMat, x, y) {
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let amt = 0
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for (let dx = -1; dx <=1; dx++) {
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for (let dy = -1; dy <= 1; dy++) {
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if (dx == 0 && dy == 0) continue
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isChair = look(stateMat, x, y, dx, dy);
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// console.log(matToString(stateMat))
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// console.log('looking from', x, y, 'in direction', dx,dy, 'chair is', isChair)
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amt += isChair
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}
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}
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return amt
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}
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function look(stateMat, x, y, dx, dy) {
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// if this is the edge, it there is no full chair
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if (x+dx < 0 || y+dy < 0 || x+dx >= stateMat[0].length|| y+dy >= stateMat.length) {return false}
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// if there is a chair, return if it is full or not
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if (layoutMat[y+dy][x+dx]) {return stateMat[y+dy][x+dx]}
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// this must be floor, check next spot
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return look(stateMat, x+dx, y+dy, dx, dy)
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}
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// convert matrix of seats into a string for logging
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function matToString (m) {
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return m.reduce((a1, r, y) => {
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return a1 +
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r.reduce((a,full,x) => a+String(full?'#':layoutMat[y][x]?'L':'.'), '') +
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'\n'},
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'');
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}
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// compare two matricies because javascript wont do that for you
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function compareMat (m1, m2) {
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return m1.reduce((a1,v1,i)=>a1&&v1.reduce((a2,v2,j)=>a2&&v2==m2[i][j],true),true)
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}
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// create matrix of false values. this is the initial state (all empty seats)
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let stateMat = new Array(layoutMat.length).fill([]).map(r => {return new Array(layoutMat[0].length).fill(false)})
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while (true) {
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prevState = stateMat.map(r => r.slice()); // deep clone the current state
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stateMat = iterate(stateMat, layoutMat); // iterate on the state
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// console.log(matToString(stateMat))
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if (compareMat(prevState, stateMat)) break // if there is no change, we are done
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}
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// log the total amount of taken seats
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console.log(stateMat.reduce((a1,b1)=>a1+b1.reduce((a2, b2)=>a2+b2, 0), 0))
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