forked from DreamCats/java-notes
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathT17.java
More file actions
107 lines (95 loc) · 2.82 KB
/
Copy pathT17.java
File metadata and controls
107 lines (95 loc) · 2.82 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
package books;
import java.util.Arrays;
/**
* @program JavaBooks
* @description: 打印从1到最大的n位数
* @author: mf
* @create: 2019/08/28 09:51
*/
/*
输入数字n，按顺序打印出从1到最大的n位十进制数。比如输入3
则打印出1、2、3一直到最大的3位数999
*/
/*
面试官没给n的范围， 万一很大呢？ int和long岂不是要溢出？
这种题溢出的题，字符串可以搞定。
*/
public class T17 {
public static void main(String[] args) {
// printToMax(2);
// printToMax2(2);
printToMax3(2);
}
// 最笨的方法，一定不符合面试官的要求
public static void printToMax(int n) {
int number = 1;
// 先求最大数
while (n-- > 0) {
number *= 10;
}
while (number-- > 1) {
System.out.println(number);
}
}
//
public static void printToMax2(int n) {
if (n <= 0) return;
char[] number = new char[n];
for (int i = 0; i < number.length; i++) {
number[i] = '0';
}
while (!Increment(number)) {
printNumber(number);
}
}
private static boolean Increment(char[] number) {
boolean isOverflow = false;
int nTakeOver = 0;
int nLength = number.length;
for (int i = nLength - 1; i >= 0; i--) {
int nSum = number[i] - '0' + nTakeOver;
if (i == nLength - 1) nSum++;
if (nSum >= 10) {
if (i == 0) isOverflow = true;
else {
nSum -= 10;
nTakeOver = 1;
number[i] = (char) ('0' + nSum);
}
} else {
number[i] = (char) ('0' + nSum);
System.out.println(number[i]);
break;
}
}
return isOverflow;
}
private static void printNumber(char[] number) {
boolean isBeginning0 = true;
int nLength = number.length;
for (int i = 0; i < nLength; i++) {
if (isBeginning0 && number[i]!= '0') isBeginning0 = false;
if(! isBeginning0) System.out.print(number[i]);
}
System.out.print('\t');
}
// 递归方法，把递归想成堆栈
public static void printToMax3(int n) {
if (n <= 0) return;
char[] number = new char[n];
for (int i = 0; i < 10; i++) {
number[0] = (char) (i + '0');
printToMax3Recur(number, n, 0);
}
}
private static void printToMax3Recur(char[] number, int n, int index) {
if (index == n - 1) {
printNumber(number);
return;
}
for (int j = 0; j < 10; j++) {
number[index + 1] = (char) (j + '0');
printToMax3Recur(number, n, index + 1);
}
}
}