ブログ記事 http://sayurin.blogspot.com/2013/12/c.html 新人女子プログラマの書いたコードを直すだけの簡単なお仕事です！｜paizaオンラインハッカソンVol.1 https://paiza.jp/poh/ec-campaign

CsPoh.cs

using System;
using System.Runtime.InteropServices;

static class CsPoh {
	static int Calculate(byte[] buffer, byte[] prices) {
		int ii = 0, oi = 0, temp;

		var itemCount = 0;
		while ((temp = buffer[ii++] - '0') >= 0)
			itemCount = itemCount * 10 + temp;
		var days = 0;
		while ((temp = buffer[ii++] - '0') >= 0)
			days = days * 10 + temp;

		do {
			var price = 0;
			while ((temp = buffer[ii++] - '0') >= 0)
				price = price * 10 + temp;
			prices[price] = 1;
		} while (--itemCount > 0);
		var low0 = 10;
		while (prices[low0] == 0)
			low0++;

		do {
			var targetPrice = 0;
			while ((temp = buffer[ii++] - '0') >= 0)
				targetPrice = targetPrice * 10 + temp;

			var low = low0;
			var high = targetPrice - low0;
			while (prices[high] == 0)
				high--;
			var price = 0;
			do {
				temp = low + high;
				if (temp == targetPrice) {
					price = targetPrice;
					break;
				}
				if (temp < targetPrice) {
					if (price < temp)
						price = temp;
					while (prices[++low] == 0)
						;
				} else
					while (prices[--high] == 0)
						;
			} while (low < high);

			if (100000 <= price)
				goto l100000;
			if (10000 <= price)
				goto l10000;
			if (1000 <= price)
				goto l1000;
			goto l100;
        l100000:
            buffer[oi++] = (byte)('0' + Math.DivRem(price, 100000, out price));
		l10000:
            buffer[oi++] = (byte)('0' + Math.DivRem(price, 10000, out price));
		l1000:
            buffer[oi++] = (byte)('0' + Math.DivRem(price, 1000, out price));
		l100:
            buffer[oi++] = (byte)('0' + Math.DivRem(price, 100, out price));
            buffer[oi++] = (byte)('0' + Math.DivRem(price, 10, out price));
			buffer[oi++] = (byte)('0' + price);
			buffer[oi++] = 10;
		} while (--days > 0);
		return oi;
	}

	[DllImport("libc")]
	static extern int read(int fd, IntPtr buf, int count);
	[DllImport("libc")]
	static extern int write(int fd, IntPtr buf, int count);

	static void Main() {
		const int valueLength = 2 + 200000 + 75;
		var buffer = new byte[valueLength * 7];
		var handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
		var pbuf = Marshal.UnsafeAddrOfPinnedArrayElement(buffer, 0);
		read(0, pbuf, valueLength * 7);
		var length = Calculate(buffer, new byte[1000001]);
		write(1, pbuf, length);
		handle.Free();
	}
}