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Finished chapter2 examples
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‎chapter2/generic_search.js

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@@ -190,7 +190,7 @@ class PriorityQueue {
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pop() {
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let root = this.heap.shift();
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this.heap.unshift(this.heap[this.heap.length - 1]);
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this.heap.unshift(this.heap[this.heap.length - 1]);
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this.heap.pop();
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this.heapify(0);
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return root;

‎chapter2/missionaries.html

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<!DOCTYPE html>
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<html>
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<head>
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<title>Missionaries and Cannibals</title>
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</head>
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<body>
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<pre>
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<script type="text/javascript" src="../util_web.js"></script>
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<script type="text/javascript" src="generic_search.js"></script>
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<script type="text/javascript" src="missionaries.js"></script>
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</pre>
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<p><a href="../index.html">Back to list</a></p>
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</body>
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</html>

‎chapter2/missionaries.js

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if (typeof window === 'undefined') {
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gs = require(__dirname + '/generic_search.js');
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util = require(__dirname + '/../util.js');
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}
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const MAX_NUM = 3;
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class MCState {
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constructor(missionaries, cannibals, boat) {
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this.wm = missionaries; // west bank missionaries
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this.wc = cannibals; // west bank cannibals
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this.em = MAX_NUM - this.wm; // east bank missionaries
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this.ec = MAX_NUM - this.wc; // east bank cannibals
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this.boat = boat; // Boat on west bank?
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}
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toString() {
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let result = "On the west bank there are " + this.wm + " missionaries ";
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result += "and " + this.wc + " cannibals.\n";
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result += "On the east bank there are " + this.em + " missionaries ";
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result += "and " + this.ec + " cannibals.\n";
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result += "The boat is on the " + (this.boat ? 'west' : 'east') + " bank.";
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return result;
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}
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goalTest() {
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return this.isLegal() && this.em === MAX_NUM && this.ec === MAX_NUM;
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}
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isLegal() {
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if (this.wm < this.wc && this.wm > 0) {
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return false;
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}
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if (this.em < this.ec && this.em > 0) {
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return false;
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}
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return true;
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}
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successors() {
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let sucs = [];
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if (this.boat) { // boat on west bank
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if (this.wm > 1) {
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sucs.push(new MCState(this.wm - 2, this.wc, !this.boat));
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}
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if (this.wm > 0) {
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sucs.push(new MCState(this.wm - 1, this.wc, !this.boat));
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}
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if (this.wc > 1) {
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sucs.push(new MCState(this.wm, this.wc - 2, !this.boat));
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}
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if (this.wc > 0) {
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sucs.push(new MCState(this.wm, this.wc - 1, !this.boat));
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}
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if (this.wc > 0 && this.wm > 0) {
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sucs.push(new MCState(this.wm - 1, this.wc - 1, !this.boat));
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}
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} else { // boat on east bank
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if (this.em > 1) {
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sucs.push(new MCState(this.wm + 2, this.wc, !this.boat));
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}
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if (this.em > 0) {
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sucs.push(new MCState(this.wm + 1, this.wc, !this.boat));
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}
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if (this.ec > 1) {
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sucs.push(new MCState(this.wm, this.wc + 2, !this.boat));
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}
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if (this.ec > 0) {
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sucs.push(new MCState(this.wm, this.wc + 1, !this.boat));
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}
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if (this.ec > 0 && this.em > 0) {
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sucs.push(new MCState(this.wm + 1, this.wc + 1, !this.boat));
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}
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}
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return sucs.filter((x) => x.isLegal());
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}
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}
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function displaySolution(path) {
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if (path.length == 0) { // sanity check
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return;
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}
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let oldState = path.shift();
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util.out(oldState.toString());
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for (currentState of path) {
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if (currentState.boat) {
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let mDiff = oldState.em - currentState.em;
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let cDiff = oldState.ec - currentState.ec;
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util.out(mDiff + " missionaries and " + cDiff + " cannibals moved from the east bank to the west bank.");
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} else {
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let mDiff = oldState.wm - currentState.wm;
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let cDiff = oldState.wc - currentState.wc;
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util.out(mDiff + " missionaries and " + cDiff + " cannibals moved from the west bank to the east bank.");
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}
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util.out(currentState.toString());
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oldState = currentState;
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}
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}
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let start = new MCState(MAX_NUM, MAX_NUM, true);
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let solution = gs.bfs(start, (mc) => mc.goalTest(), (mc) => mc.successors());
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if (solution == null) {
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util.out("No solution found!");
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} else {
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let path = gs.nodeToPath(solution);
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displaySolution(path);
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}

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