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5.21: floyd, graph, shortest path(파티)
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// 파티 : 최단 경로, 그래프 | ||
const input = require("fs") | ||
.readFileSync("/dev/stdin") | ||
.toString() | ||
.trim() | ||
.split("\n") | ||
.map((v) => v.split(" ").map((v) => Number(v))); | ||
const [n, m, x] = input.shift(); | ||
const edges = input; | ||
const times = new Array(n + 1) | ||
.fill(null) | ||
.map(() => new Array(n + 1).fill(Infinity)); | ||
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for (const [start, end, time] of edges) { | ||
times[start][end] = time; | ||
} | ||
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// j -> i -> k(i -> j -> k가 아님) | ||
for (let layover = 1; layover <= n; layover++) { | ||
for (let start = 1; start <= n; start++) { | ||
for (let end = 1; end <= n; end++) { | ||
// times[layover][end] = Math.min(times[layover][end], times[layover][start] + times[start][end]); | ||
times[start][end] = Math.min( | ||
times[start][end], | ||
times[start][layover] + times[layover][end] | ||
); | ||
} | ||
} | ||
} | ||
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let max = 0; | ||
for (let i = 1; i <= n; i++) { | ||
if (i === x) { | ||
continue; | ||
} | ||
max = Math.max(max, times[i][x] + times[x][i]); | ||
} | ||
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console.log(max); | ||
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// n이 최대 1000이기 때문에 다익스트라, 플로이드 어느 것을 사용해도 됨 | ||
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// i -> j -> k : i에서 j를 거쳐 k로 가는 방법 | ||
// j -> i -> k : j에서 i를 거쳐 k로 가는 방법(이게 정답, 헷갈리지 않게 주의) | ||
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// i, j, k 대신 layover, start, end로 기억하기 |