23 lines
610 B
JavaScript
23 lines
610 B
JavaScript
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const fs = require('fs');
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let rules = fs.readFileSync('input.txt', 'utf-8').split('\n');
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steps = [];
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for (let rule of rules) {
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[_, step1, step2] = rule.match(/Step (\w) must be finished before step (\w) can begin./);
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if (!steps[step1])
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steps[step1] = []
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if (!steps[step2])
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steps[step2] = []
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steps[step2].push(step1)
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}
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let ans = '';
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while (Object.entries(steps).length > 0) {
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let step = Object.entries(steps).filter(v => v[1].length == 0).map(v => v[0]).sort()[0]
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delete steps[step];
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for (let step_ in steps) {
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steps[step_] = steps[step_].filter(v => v != step)
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}
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ans += step
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}
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console.log(ans)
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