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Copy pathBusRoutes.js
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57 lines (47 loc) · 1.54 KB
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// https://leetcode-cn.com/problems/bus-routes/
var Test = require('../Common/Test');
var numBusesToDestination = function (routes, start, target) {
if (start == target) return 0;
routes = routes.map(a => new Set(a));
const starts = [];
const targets = new Set();
for (let i = 0; i < routes.length; i++) {
const route = routes[i];
if (route.has(start)) starts.push(i);
if (route.has(target)) targets.add(i);
}
const indexSet = new Set(Array(routes.length).keys());
const steps = Array(routes.length).fill(Infinity);
for (const i of starts) {
indexSet.delete(i);
steps[i] = 1;
}
const queue = starts;
while (queue.length > 0 && !targets.has(queue[0])) {
const index = queue.shift();
const queueLength = queue.length;
const step = steps[index] + 1;
const set = routes[index];
for (const i of indexSet) {
if (hasIntersection(set, routes[i])) {
steps[i] = step;
queue.push(i);
}
}
for (let i = queueLength; i < queue.length; i++) {
indexSet.delete(queue[i]);
}
}
return queue.length > 0 ? steps[queue[0]] : -1;
function hasIntersection(set1, set2) {
for (const e of set1) {
if (set2.has(e)) return true;
}
return false;
}
};
function test(routes, start, target) {
Test.test(numBusesToDestination, routes, start, target);
}
// test([[1, 2, 7], [3, 6, 7]], 1, 6);
test([[1, 7], [3, 5]], 5, 5);