CodeIQ「中学入試から：概数と計算」解答コード

GaisuToKesan.java

// GaisuToKesan.java
import java.util.Scanner;
import java.math.BigDecimal;
import java.math.MathContext;

class GaisuToKesan {
	// 答えを格納するリストのクラス
	private static class AnswerList {
		private String answer;
		private AnswerList nextAnswer;
		public AnswerList() {
			this(null);
		}
		public AnswerList(String answer) {
			this.answer = answer;
			this.nextAnswer = null;
		}
		public void setNextAnswer(AnswerList nextAnswer) {
			this.nextAnswer = nextAnswer;
		}
		public AnswerList getNextAnswer() {
			return this.nextAnswer;
		}
		public String getAnswer() {
			return answer;
		}
	}

	private static class Range {
		public BigDecimal min, max;
		public boolean includeMin, includeMax;
	}

	// 操作を元に戻す
	private static Range getRange(BigDecimal value, int digit, String operation) {
		BigDecimal delta = BigDecimal.ONE.divide(BigDecimal.TEN.pow(digit));
		Range ret = null;
		if (operation.equals("四捨五入")) {
			ret = new Range();
			ret.min = value.subtract(delta.multiply(new BigDecimal(5)));
			ret.includeMin = true;
			ret.max = value.add(delta.multiply(new BigDecimal(5)));
			ret.includeMax = false;
		} else if (operation.equals("切り上げ")) {
			ret = new Range();
			ret.min = value.subtract(delta.multiply(BigDecimal.TEN));
			ret.includeMin = false;
			ret.max = value;
			ret.includeMax = true;
		} else if (operation.equals("切り捨て")) {
			ret = new Range();
			ret.min = value;
			ret.includeMin = true;
			ret.max = value.add(delta.multiply(BigDecimal.TEN));
			ret.includeMax = false;
		}
		return ret;
	}

	// 余分なゼロを消す
	private static String zeroSuppress(String value) {
		if (value == null || value.indexOf('.') < 0) return value;
		return value.replaceFirst("\\.?0+$", "");
	}

	public static String solve(String[] query, String id) {
		int digit1 = Integer.parseInt(query[0]);
		String operation1 = query[1];
		BigDecimal multiplier = new BigDecimal(query[2]);
		int digit2 = Integer.parseInt(query[3]);
		String operation2 = query[4];
		BigDecimal calcResult = new BigDecimal(query[5]);
		// 計算する桁数(わからないので余裕を持たせる)
		int enoughDigit = (digit1 >= digit2 ? digit1 : digit2) * 100;
		MathContext mc = new MathContext(enoughDigit);

		if (multiplier.signum() <= 0 || calcResult.signum() < 0) {
			return "負数は非対応です";
		}
		if (digit1 <= 0 || digit2 <= 0) {
			return "桁数が不正です";
		}

		// 最後の操作を元に戻す
		BigDecimal number2rem = BigDecimal.ONE.divide(BigDecimal.TEN.pow(digit2 - 1));
		if (calcResult.remainder(number2rem).compareTo(BigDecimal.ZERO) != 0) {
			// 例 : 小数第1位を切り捨てすると0.24になる数は存在しない(T10)
			if (id != null) {
				System.err.println("警告 : " + id + "で後の" + operation2 + "の結果が不正です");
			}
			return "なし";
			//return "後の" + operation2 + "の結果が不正です";
		}
		Range range = getRange(calcResult, digit2, operation2);
		if (range == null) {
			return "後の演算の種類が不正です";
		}

		// 掛け算を元に戻す
		range.min = range.min.divide(multiplier, mc);
		range.max = range.max.divide(multiplier, mc);

		// 最初の操作後の範囲を求める
		BigDecimal number1 = BigDecimal.ONE.divide(BigDecimal.TEN.pow(digit1 - 1));
		BigDecimal rangeMinRemainder, rangeMaxRemainder;
		rangeMinRemainder = range.min.remainder(number1);
		rangeMaxRemainder = range.max.remainder(number1);
		if (rangeMinRemainder.compareTo(BigDecimal.ZERO) != 0) {
			range.min = range.min.subtract(rangeMinRemainder).add(number1);
			range.includeMin = true;
		}
		if (rangeMaxRemainder.compareTo(BigDecimal.ZERO) != 0) {
			range.max = range.max.subtract(rangeMaxRemainder);
			range.includeMax = true;
		}
		// さらに範囲を調整する
		if (!range.includeMin) {
			range.min = range.min.add(number1);
		}
		if (!range.includeMax) {
			range.max = range.max.subtract(number1);
		}

		// 最終的な範囲を決定する
		Range minRange = getRange(range.min, digit1, operation1);
		Range maxRange = getRange(range.max, digit1, operation1);
		int compare = minRange.min.compareTo(maxRange.max);
		if (compare > 0 || (compare == 0 && (!minRange.includeMin || !maxRange.includeMax))) {
			return "なし";
		} else {
			return zeroSuppress(minRange.min.toPlainString()) +
				(minRange.includeMin ? "以上" : "より大きく") +
				zeroSuppress(maxRange.max.toPlainString()) +
				(maxRange.includeMax ? "以下" : "未満");
		}
	}

	public static void main(String args[]) {
		boolean testMode = false;
		boolean warnForInvalidResult = false;
		for (int i = 0; i < args.length; i++) {
			if (args[i].equals("--test") || args[i].equals("-t")) {
				testMode = true;
			} else if (args[i].equals("--warn") || args[i].equals("-w")) {
				warnForInvalidResult = true;
			}
		}

		Scanner sc = new Scanner(System.in);
		AnswerList answerNode = null;
		AnswerList lastAnswerNode = null;
		while(sc.hasNextLine()) {
			// データを読み込む
			String[] lineData = sc.nextLine().split("\t");
			if (lineData.length != 8) continue;
			String id = lineData[0];
			String expectedAnswer = lineData[7];
			String[] query = new String[6];
			for (int i = 0; i < 6; i++) query[i] = lineData[i + 1];
			if (testMode && !id.startsWith("T")) continue;
			// 問題を解く
			String answer;
			try {
				answer = solve(query, warnForInvalidResult ? id : null);
			} catch(Exception e) {
				answer = e.toString();
				e.printStackTrace();
			}
			// 一致していなければリストに加える
			if (!expectedAnswer.equals(answer)) {
				System.err.println(id + " : expected " + expectedAnswer + ", got " + answer);
				AnswerList nextAnswer = new AnswerList(id);
				if (lastAnswerNode == null) {
					// リストの先頭を設定する
					answerNode = lastAnswerNode = nextAnswer;
				} else {
					// リストの末尾に追加する
					lastAnswerNode.setNextAnswer(nextAnswer);
					lastAnswerNode = nextAnswer;
				}
			}
		}
		System.err.println();
		// 結果を出力する
		if (answerNode != null) {
			int answerCount = 1;
			System.out.print(answerNode.getAnswer());
			for (AnswerList itr = answerNode.getNextAnswer(); itr != null; itr = itr.getNextAnswer()) {
				System.out.print("," + itr.getAnswer());
				answerCount++;
			}
			System.out.println();
			System.err.println("" + answerCount + " mismatch(es) found.");
		}
	}
}