--wip-- [skip ci]

Author: amejiarosario

lab/exercises/10-mixed/critical-connections-1.js

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+/**
+ * @param {number} n
+ * @param {number[][]} connections
+ * @return {number[][]}
+ */
+function criticalConnections(n, connections) {
+  const critical = [];
+  const graph = buildGraph(n, connections);
+  // console.log({graph})
+
+  for (let i = 0; i < connections.length; i++) { // O(|E| * [|V|^3 + |V|^2|E|]) = O(|V|^3|E| + |V|^2|E|^2)
+    const link = connections[i];
+    if (isLinkCritical(link, graph)) {
+      critical.push(link);
+    }
+  }
+
+  return critical;
+}
+
+function buildGraph(n, connections) {
+  const graph = [...Array(n).keys()].reduce((map, i) => {
+    map.set(i, new Set());
+    return map;
+  }, new Map());
+
+  connections.forEach(([i, j]) => {
+    const iAdj = graph.get(i);
+    iAdj.add(j);
+    const jAdj = graph.get(j);
+    jAdj.add(i);
+  });
+
+  return graph;
+}
+
+function isLinkCritical(link, graph) { // DFS: O(|V|^2 * |E|+|V|) = O(|V|^3 + |V|^2|E|)
+  for (let i = 0; i < graph.size; i++) {
+    for (let j = 0; j < graph.size; j++) {
+      if (hasLink([i, j], link)) continue;
+      if (!isConnected(i, j, link, graph)) { // DFS: O(|E|+|V|)
+        // console.log({i, j, link});
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+function hasLink(a, b) {
+  return (a[0] === b[0] && a[1] === b[1]) || (a[0] === b[1] && a[1] === b[0]);
+}
+
+// DFS: O(|E|+|V|)
+function isConnected(i, j, ignoreLink, graph, seen = new Set()) {
+  if (i === j) return true;
+  if (graph.get(i).has(j)) return true;
+
+  for (const adj of graph.get(i)) {
+    if (hasLink([i, adj], ignoreLink)) continue;
+
+    if (seen.has(adj)) continue;
+    seen.add(adj);
+
+    if (isConnected(adj, j, ignoreLink, graph, seen)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+module.exports = criticalConnections;

lab/exercises/10-mixed/critical-connections.data.js

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+/**
+ * @param {number} n
+ * @param {number[][]} connections
+ * @return {number[][]}
+ */
+function criticalConnections(n, connections) {
+  const graph = buildGraph(n, connections);
+  // console.log({graph})
+
+  return dfs(graph, 0);
+}
+
+
+function buildGraph(n, connections) {
+  const graph = [...Array(n).keys()].reduce((map, i) => {
+    map.set(i, new Set());
+    return map;
+  }, new Map());
+
+  connections.forEach(([i, j]) => {
+    const iAdj = graph.get(i);
+    iAdj.add(j);
+    const jAdj = graph.get(j);
+    jAdj.add(i);
+  });
+
+  return graph;
+}
+
+function dfs(graph, current, previous = null, rank = 1, group = []) {
+  let criticalLinks = [];
+  group[current] = rank;
+
+  for (const adj of graph.get(current)) {
+    if (adj === previous) continue;
+
+    if (!group[adj]) { // if not visited (and not in a group yet)
+      const links = dfs(graph, adj, current, rank + 1, group);
+      if (links.length) {
+        criticalLinks = criticalLinks.concat(links);
+      }
+    }
+
+    group[current] = Math.min(group[current], group[adj]);
+
+    if (group[adj] >= rank + 1) {
+      criticalLinks.push([current, adj]);
+    }
+  }
+
+  return criticalLinks;
+}
+
+module.exports = criticalConnections;

lab/exercises/10-mixed/critical-connections.js

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+const assert = require('assert');
+
+// const criticalConnections = require('./critical-connections');
+const criticalConnections = require('./critical-connections');
+const data = require('./critical-connections.data');
+
+assert.deepEqual(criticalConnections(4, [
+  [0, 1],
+  [1, 2],
+  [2, 0],
+  [1, 3],
+]), [[1, 3]]);
+
+const { n, connections } = data.test1000;
+assert.deepEqual(criticalConnections(n, connections), []);
+
+console.log('All tests passed!');

lab/exercises/10-mixed/critical-connections.runner.js

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+// npx jest lab/exercises/10-mixed/critical-connections.spec.js --watch
+const criticalConnections = require('./critical-connections');
+
+describe('Critical Connections', () => {
+  it('should work with 4 nodes', () => {
+    const n = 4;
+    const connections = [
+      [0, 1],
+      [1, 2],
+      [2, 0],
+      [1, 3],
+    ];
+    expect(criticalConnections(n, connections)).toEqual([
+      [1, 3],
+    ]);
+  });
+
+  it('should work with nodes in line (all critical)', () => {
+    const n = 4;
+    const connections = [
+      [0, 1],
+      [1, 2],
+      [2, 3],
+    ];
+    expect(criticalConnections(n, connections)).toEqual(expect.arrayContaining([
+      [0, 1],
+      [1, 2],
+      [2, 3],
+    ]));
+  });
+
+  it('should work with nodes in daisy chain (no critical)', () => {
+    const n = 4;
+    const connections = [
+      [0, 1],
+      [1, 2],
+      [2, 3],
+      [3, 0],
+    ];
+    expect(criticalConnections(n, connections)).toEqual(expect.arrayContaining([]));
+  });
+});

lab/exercises/10-mixed/critical-connections.spec.js

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+// npx jest lab/exercises/10-mixed/integer-to-words.spec.js --watch
+
+const map = {
+  0: 'Zero',
+  1: 'One',
+  2: 'Two',
+  3: 'Three',
+  4: 'Four',
+  5: 'Five',
+  6: 'Six',
+  7: 'Seven',
+  8: 'Eight',
+  9: 'Nine',
+  10: 'Ten',
+  11: 'Eleven',
+  12: 'Twelve',
+  13: 'Thirteen',
+  14: 'Fourteen',
+  15: 'Fifteen',
+  16: 'Sixteen',
+  17: 'Seventeen',
+  18: 'Eighteen',
+  19: 'Nineteen',
+  20: 'Twenty', // Twenty One
+
+  30: 'Thirty', // Thirty Four
+  40: 'Forty',
+  50: 'Fifty',
+  60: 'Sixty', // Sixty Seven
+  70: 'Seventy',
+  80: 'Eighty',
+  90: 'Ninety',
+  100: 'Hundred', // One Hundred, Two Hundred
+
+  1_000: 'Thousand', // Four Thousand
+
+  1_000_000: 'Million', // One Million
+
+  1_000_000_000: 'Billion', // One Billion
+};
+
+const keys = [
+  // 1_000_000_000,
+  // 1_000_000,
+  // 1_000,
+  // 100,
+  10,
+];
+
+/**
+ * @param {number} num
+ * @return {string}
+ * @pomodoro II
+ */
+function numberToWords(num) {
+  if (num < 21) return map[num];
+
+  let ans = [];
+//   let i = 0;
+
+//   while (num && i < keys.length) {
+//     // const div = keys[i++]; // 10
+//     const div = 10;
+//     const reminder = num % div; // 1
+//     const left = num - reminder; // 20
+
+//     if (left && map[left] !== undefined) {
+//       ans.push(map[left]);
+//       num -= left;
+//     }
+
+//     num = reminder;
+//   }
+  ans = ans.concat(numberToWords(Math.floor(num/10) * 10));
+  ans = ans.concat(numberToWords(Math.floor(num % 10)))
+
+  return ans.join(' ');
+};
+
+// convert a number into its English representation
+
+// 21
+// Twenty One
+
+// 1_234_567_891
+
+console.log(process.version);
+
+module.exports = numberToWords;

lab/exercises/10-mixed/integer-to-words.js

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+/*eslint-disable */
+const assert = require('assert');
+
+const numberToWords = require('./integer-to-words');
+
+assert.equal(numberToWords(0), 'Zero');
+assert.equal(numberToWords(1), 'One');
+assert.equal(numberToWords(20), 'Twenty');
+assert.equal(numberToWords(21), 'Twenty One');
+assert.equal(numberToWords(99), 'Ninety Nine');
+
+console.log('All tests passed!');

lab/exercises/10-mixed/integer-to-words.spec-assert.js

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+const numberToWords = require('./integer-to-words');
+
+describe('Integer to English Words', () => {
+  it('should convert 0', () => {
+    expect(numberToWords(0)).toEqual('Zero');
+  });
+});

lab/exercises/10-mixed/integer-to-words.spec.js

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+/**
+ * Compute how much water it is able to trap after raining.
+ * @param {number[]} height Non-negative integers representing
+ *  an elevation map where the width of each bar is 1.
+ *
+ * @runtime O(n^2) - Brute force
+ * @space O(1)
+ */
+function trap(height) {
+  let ans = 0;
+
+  for (let i = 0; i < height.length; i++) {
+    let leftMax = 0;
+    let rightMax = 0;
+    for (let j = i; j >= 0; j--) {
+      leftMax = Math.max(leftMax, height[j]);
+    }
+    for (let j = i; j < height.length; j++) {
+      rightMax = Math.max(rightMax, height[j]);
+    }
+
+    ans += Math.min(leftMax, rightMax) - height[i];
+  }
+
+  return ans;
+}
+
+module.exports = trap;

lab/exercises/10-mixed/trapping-rain-water-1.js

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+/**
+ * Compute how much water it is able to trap after raining.
+ * @param {number[]} height Non-negative integers representing
+ *  an elevation map where the width of each bar is 1.
+ *
+ * @runtime O(n) - using DP
+ * @space O(n)
+ */
+function trap(height) {
+  let ans = 0;
+  const leftMax = [];
+  const rightMax = [];
+
+  for (let j = height.length - 1; j >= 0; j--) {
+    leftMax[j] = Math.max((leftMax[j + 1] || 0), height[j]);
+  }
+  for (let j = 0; j < height.length; j++) {
+    rightMax[j] = Math.max((rightMax[j - 1] || 0), height[j]);
+  }
+
+  for (let i = 0; i < height.length; i++) {
+    ans += Math.min(leftMax[i], rightMax[i]) - height[i];
+  }
+
+  return ans;
+}
+
+module.exports = trap;