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// 도시 분할 계획 : 그래프, 최소 스패닝 트리 | ||
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 edges = input; | ||
const parentArr = new Array(n + 1).fill(null).map((_v, i) => i); | ||
let answer = 0; | ||
let cnt = n; | ||
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function getParent(x, parentArr) { | ||
if (parentArr[x] === x) return x; | ||
else return getParent(parentArr[x], 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); | ||
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 (cnt === 2) break; | ||
if (find(start, end, parentArr)) continue; | ||
union(start, end, parentArr); | ||
answer += cost; | ||
// parentArr[x] = x가 아닌 개수 | ||
// 직접 parentArr에서 x가 아닌 개수를 세면 시간 초과 | ||
cnt--; | ||
} | ||
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console.log(answer); |