[oh-chaeyeon] 25.02.20

oh-chaeyeon/7주차_그래프/Find_Center_of_Star_Graph.js

@@ -0,0 +1,9 @@
+/**
+ * @param {number[][]} edges
+ * @return {number}
+ */
+var findCenter = function (edges) {
+  return edges[0][0] === edges[1][0] || edges[0][0] === edges[1][1]
+    ? edges[0][0]
+    : edges[0][1];
+};

oh-chaeyeon/7주차_그래프/Find_if_Path_Exists_in_Graph.js

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+/**
+ * @param {number} n
+ * @param {number[][]} edges
+ * @param {number} source
+ * @param {number} destination
+ * @return {boolean}
+ */
+var validPath = function (n, edges, source, destination) {
+  const graph = Array.from({ length: n }, () => []);
+
+  edges.forEach(([u, v]) => {
+    graph[u].push(v);
+    graph[v].push(u);
+  });
+
+  const visited = new Set();
+
+  const dfs = (node) => {
+    if (node === destination) return true;
+    visited.add(node);
+
+    for (const neighbor of graph[node]) {
+      if (!visited.has(neighbor) && dfs(neighbor)) {
+        return true;
+      }
+    }
+
+    return false;
+  };
+
+  return dfs(source);
+};

oh-chaeyeon/7주차_그래프/Find_the_Town_Judge.js

@@ -0,0 +1,21 @@
+/**
+ * @param {number} n
+ * @param {number[][]} trust
+ * @return {number}
+ */
+var findJudge = function (n, trust) {
+  const trustCount = new Array(n + 1).fill(0);
+
+  for (const [a, b] of trust) {
+    trustCount[a]--;
+    trustCount[b]++;
+  }
+
+  for (let i = 1; i <= n; i++) {
+    if (trustCount[i] === n - 1) {
+      return i;
+    }
+  }
+
+  return -1;
+};

oh-chaeyeon/7주차_그래프/게임_맵_최단거리.js

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+function solution(maps) {
+  const n = maps.length;
+  const m = maps[0].length;
+  const directions = [
+    [1, 0],
+    [-1, 0],
+    [0, 1],
+    [0, -1],
+  ];
+  const queue = [[0, 0]];
+  const visited = Array.from({ length: n }, () => Array(m).fill(false));
+  visited[0][0] = true;
+  let count = 1;
+
+  while (queue.length > 0) {
+    const size = queue.length;
+    for (let i = 0; i < size; i++) {
+      const [x, y] = queue.shift();
+
+      if (x === n - 1 && y === m - 1) {
+        return count;
+      }
+
+      for (const [dx, dy] of directions) {
+        const nx = x + dx;
+        const ny = y + dy;
+
+        if (
+          nx >= 0 &&
+          ny >= 0 &&
+          nx < n &&
+          ny < m &&
+          maps[nx][ny] === 1 &&
+          !visited[nx][ny]
+        ) {
+          visited[nx][ny] = true;
+          queue.push([nx, ny]);
+        }
+      }
+    }
+    count++;
+  }
+
+  return -1;
+}

oh-chaeyeon/7주차_그래프/배달.js

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+function solution(N, road, K) {
+  const graph = Array.from({ length: N + 1 }, () => []);
+
+  for (const [a, b, c] of road) {
+    graph[a].push([b, c]);
+    graph[b].push([a, c]);
+  }
+
+  const distances = Array(N + 1).fill(Infinity);
+  distances[1] = 0;
+  const priorityQueue = [[0, 1]];
+
+  while (priorityQueue.length > 0) {
+    const [currentDistance, currentNode] = priorityQueue.shift();
+
+    if (currentDistance > distances[currentNode]) {
+      continue;
+    }
+
+    for (const [neighbor, time] of graph[currentNode]) {
+      const newDistance = currentDistance + time;
+      if (newDistance < distances[neighbor]) {
+        distances[neighbor] = newDistance;
+        priorityQueue.push([newDistance, neighbor]);
+        priorityQueue.sort((a, b) => a[0] - b[0]);
+      }
+    }
+  }
+
+  return distances.filter((distance) => distance <= K).length;
+}

oh-chaeyeon/7주차_그래프/전력망을_돌로_나누기.js

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+function solution(n, wires) {
+  const graph = Array.from({ length: n + 1 }, () => []);
+
+  for (const [v1, v2] of wires) {
+    graph[v1].push(v2);
+    graph[v2].push(v1);
+  }
+
+  let minDifference = Number.MAX_VALUE;
+
+  const dfs = (node, visited) => {
+    let count = 1;
+    visited[node] = true;
+
+    for (const neighbor of graph[node]) {
+      if (!visited[neighbor]) {
+        count += dfs(neighbor, visited);
+      }
+    }
+
+    return count;
+  };
+
+  for (const [v1, v2] of wires) {
+    const visited = Array(n + 1).fill(false);
+    visited[v1] = true;
+    const count = dfs(v2, visited);
+    const difference = Math.abs(count - (n - count));
+    minDifference = Math.min(minDifference, difference);
+  }
+
+  return minDifference;
+}

oh-chaeyeon/7주차_그래프/타켓_넘버.js

@@ -0,0 +1,18 @@
+function solution(numbers, target) {
+  const dp = new Map();
+  dp.set(0, 1);
+
+  for (const number of numbers) {
+    const nextDp = new Map();
+    for (const [sum, count] of dp) {
+      nextDp.set(sum + number, (nextDp.get(sum + number) || 0) + count);
+      nextDp.set(sum - number, (nextDp.get(sum - number) || 0) + count);
+    }
+    dp.clear();
+    for (const [sum, count] of nextDp) {
+      dp.set(sum, count);
+    }
+  }
+
+  return dp.get(target) || 0;
+}