print1ToMaxOfNDigits

Author: yangrubing

swordForOffer/src/main/java/problem12/Print1ToMaxOfNDigits.java

@@ -0,0 +1,86 @@
+package problem12;
+
+/**
+ * 打印1到最大的n位数，如输入3，则打印1，2，3，。。。。，999
+ * 思路：大数，如果面试题是关于n位的整数并且没有限定n的取值范围，或者输入任意大小的整数，则要考虑用
+ * 字符串来模拟大数问题
+ * Created by bjyangrubing on 2016/8/16.
+ */
+public class Print1ToMaxOfNDigits
+{
+	public void print1ToMaxOfNDigits(int n)
+	{
+		if (n <= 0)
+			return;
+		char[] numbers = new char[n];
+		//初始化numbers为0
+		for (int i = 0; i < numbers.length; i++)
+		{
+			numbers[i] = '0';
+		}
+		while (!increment(numbers))//如果没有overFlow
+		{
+			printNumbers(numbers);
+		}
+
+	}
+
+	/**
+	 * 打印的函数
+	 * @param numbers
+	 */
+	private void printNumbers(char[] numbers)
+	{
+		boolean isBeginning0 = true;
+		for (int i = 0; i < numbers.length; i++)
+		{
+			if (numbers[i] != '0')
+				isBeginning0 = false;
+			if (!isBeginning0)
+			{
+				System.out.print(numbers[i]);
+			}
+		}
+
+		System.out.println();
+	}
+
+	private boolean increment(char[] numbers)
+	{
+		boolean isOverFlow = false;
+		int nTakeOver = 0;//第n位的进位，有则为0
+		int nLength = numbers.length;
+		for (int i = nLength - 1; i >= 0; i--)
+		{
+			int nSum = numbers[i] - '0' + nTakeOver;//第n位的和
+			if (i == nLength - 1)//如果是个位，则+1
+				nSum += 1;
+			if (nSum >= 10)//加完以后大于10
+			{//如果末位的数值大于10
+				if (i == 0)
+				{//如果是最高位
+					isOverFlow = true;
+				}
+				else
+				{//否则设置为有进位，并且把值设置为'0'
+					nSum -= 10;
+					nTakeOver = 1;
+					numbers[i] = (char) ('0' + nSum);
+				}
+			}
+			else
+			{//否则，直接赋值并且break
+				numbers[i] = (char) (nSum + '0');
+				break;
+			}
+		}
+		return isOverFlow;
+	}
+
+	public static void main(String[] args)
+	{
+		Print1ToMaxOfNDigits p = new Print1ToMaxOfNDigits();
+		p.print1ToMaxOfNDigits(3);
+	}
+
+}

swordForOffer/src/test/java/problem12/Print1ToMaxOfNDigitsTest.java

@@ -0,0 +1,16 @@
+package problem12;
+
+import org.junit.Test;
+
+/**
+ * Created by bjyangrubing on 2016/8/16.
+ */
+public class Print1ToMaxOfNDigitsTest
+{
+	@Test
+	public void test()
+	{
+		Print1ToMaxOfNDigits p = new Print1ToMaxOfNDigits();
+		p.print1ToMaxOfNDigits(3);
+	}
+}