Maxim Dolgolyov
89 lines
3.5 KiB
JavaScript
89 lines
3.5 KiB
JavaScript
'use strict';
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/* ──────────────────────────────────────────────────────────────────
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Answer normalization + correctness check.
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Same algorithm runs on user input and stored canonical answer
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(from /tasks endpoint), then compared.
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Canonical answer forms (produced by backend/scripts/import-exam-tasks.js):
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MC: single Cyrillic letter: "а" | "б" | "в" | "г" | "д"
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open NUM: decimal: "-2" "7500" "1.5" "0.25"
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open FRAC: fraction: "9/4" "-104/9" (sign on numerator)
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open PAIR: two values, ";" sep: "-2;4"
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The user can type the answer in many equivalent forms — the normalizer
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accepts any form and decides equivalence numerically.
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────────────────────────────────────────────────────────────────── */
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(function () {
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const EPS = 1e-6;
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// Try to coerce a string to a number; returns NaN on failure.
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function toNumber(s) {
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if (s == null) return NaN;
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let t = String(s).trim().replace(/\$/g, '').replace(/\s+/g, '').replace(',', '.');
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// Fraction "a/b" → a/b
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const f = t.match(/^(-?\d+(?:\.\d+)?)\s*\/\s*(-?\d+(?:\.\d+)?)$/);
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if (f) {
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const num = Number(f[1]);
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const den = Number(f[2]);
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if (!Number.isFinite(num) || !Number.isFinite(den) || den === 0) return NaN;
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return num / den;
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}
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const n = Number(t);
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return Number.isFinite(n) ? n : NaN;
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}
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// Parse a "pair" answer "A;B" — accepts ";" or "," or " и " or whitespace
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function toPair(s) {
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if (s == null) return null;
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const t = String(s).trim().replace(/\$/g, '').replace(/\s+и\s+/g, ';');
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const parts = t.split(/[;,]/).map(p => p.trim()).filter(Boolean);
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if (parts.length !== 2) return null;
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const a = toNumber(parts[0]);
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const b = toNumber(parts[1]);
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if (Number.isNaN(a) || Number.isNaN(b)) return null;
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// Order-insensitive comparison: return sorted pair
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return a <= b ? [a, b] : [b, a];
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}
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/* Detect form of the canonical answer.
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Returns: 'mc' | 'pair' | 'numeric' */
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function detectForm(canonical) {
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if (canonical == null) return 'numeric';
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const t = String(canonical).trim();
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if (/^[а-д]$/.test(t)) return 'mc';
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if (/^[^;]+;[^;]+$/.test(t)) return 'pair';
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return 'numeric';
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}
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/* Main check. Returns true iff user input matches canonical answer.
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False if either side can't be normalized.
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Both inputs are strings as returned by the form or stored in DB. */
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function check(userInput, canonical) {
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if (userInput == null || canonical == null) return false;
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const form = detectForm(canonical);
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if (form === 'mc') {
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const u = String(userInput).trim().toLowerCase();
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return u === String(canonical).trim().toLowerCase();
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}
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if (form === 'pair') {
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const cp = toPair(canonical);
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const up = toPair(userInput);
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if (!cp || !up) return false;
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return Math.abs(cp[0] - up[0]) < EPS && Math.abs(cp[1] - up[1]) < EPS;
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}
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// Numeric (integer / decimal / fraction)
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const c = toNumber(canonical);
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const u = toNumber(userInput);
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if (Number.isNaN(c) || Number.isNaN(u)) return false;
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return Math.abs(c - u) < EPS;
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}
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window.EP = window.EP || {};
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window.EP.answer = { check, detectForm, toNumber, toPair };
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})();
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