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// 다리 만들기 2 : 브루트 포스, 그래프, 최소 스패닝 트리, 깊이 우선 탐색 | ||
const input = require("fs") | ||
.readFileSync("/dev/stdin") | ||
.toString() | ||
.trim() | ||
.split("\n") | ||
.map((v) => v.split(" ").map((v) => parseInt(v, 10))); | ||
const [n, m] = input.shift(); | ||
const map = input.map((v) => v.map((v) => (v === 0 ? 0 : 9))); | ||
const dir = [ | ||
[0, -1], | ||
[1, 0], | ||
[0, 1], | ||
[-1, 0], | ||
]; | ||
let count = 1; | ||
|
||
function dfs(x, y, count) { | ||
if (x < 0 || x >= n || y < 0 || y >= m) return; | ||
if (map[x][y] === 9) { | ||
map[x][y] = count; | ||
} else return; | ||
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for (let i = 0; i < dir.length; i++) { | ||
dfs(x + dir[i][0], y + dir[i][1], count); | ||
} | ||
} | ||
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// dfs로 섬 카운트 | ||
for (let i = 0; i < n; i++) { | ||
for (let j = 0; j < m; j++) { | ||
if (map[i][j] === 9) { | ||
dfs(i, j, count); | ||
count++; | ||
} | ||
} | ||
} | ||
count--; | ||
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// 섬의 모든 곳에서 네 방향으로 탐색하며 최단 거리 계산 | ||
const costs = new Array(count) | ||
.fill(null) | ||
.map(() => new Array(count).fill(Infinity)); | ||
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for (let i = 0; i < n; i++) { | ||
for (let j = 0; j < m; j++) { | ||
if (map[i][j] !== 0) { | ||
// 네 방향으로 탐색 | ||
for (let k = 0; k < dir.length; k++) { | ||
let length = 0; | ||
let startX = i + dir[k][0], | ||
startY = j + dir[k][1]; | ||
while ( | ||
!(startX < 0 || startX >= n || startY < 0 || startY >= m) && | ||
map[startX][startY] === 0 | ||
) { | ||
startX += dir[k][0]; | ||
startY += dir[k][1]; | ||
length++; | ||
} | ||
if (length >= 2) { | ||
if (!(startX < 0 || startX >= n || startY < 0 || startY >= m)) { | ||
costs[map[i][j] - 1][map[startX][startY] - 1] = Math.min( | ||
costs[map[i][j] - 1][map[startX][startY] - 1], | ||
length | ||
); | ||
costs[map[startX][startY] - 1][map[i][j] - 1] = Math.min( | ||
costs[map[startX][startY] - 1][map[i][j] - 1], | ||
length | ||
); | ||
} | ||
} | ||
} | ||
} | ||
} | ||
} | ||
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// 크루스칼 알고리즘으로 최단 거리의 합 계산 | ||
const edges = []; | ||
let answer = 0; | ||
const parentArr = new Array(count + 1).fill(null).map((_v, i) => i); | ||
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for (let i = 0; i < count; i++) { | ||
for (let j = i; j < count; j++) { | ||
if (costs[i][j] !== Infinity) edges.push([i + 1, j + 1, costs[i][j]]); | ||
} | ||
} | ||
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function getParent(a, parentArr) { | ||
if (parentArr[a] === a) return a; | ||
else return getParent(parentArr[a], parentArr); | ||
} | ||
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function union(a, b, parentArr) { | ||
a = getParent(a, parentArr); | ||
b = getParent(b, parentArr); | ||
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if (a > b) parentArr[a] = b; | ||
else parentArr[b] = a; | ||
} | ||
|
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function find(a, b, parentArr) { | ||
a = getParent(a, parentArr); | ||
b = getParent(b, parentArr); | ||
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return a === b; | ||
} | ||
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const sorted = edges.sort((a, b) => a[2] - b[2]); | ||
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for (let [start, end, cost] of sorted) { | ||
if (!find(start, end, parentArr)) { | ||
union(start, end, parentArr); | ||
count--; | ||
answer += cost; | ||
} | ||
} | ||
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console.log(count === 1 ? answer : -1); |