JZ29 顺时针打印矩阵
1 /* 模拟 */
2 public class JZ29_1
3 {
4 public static ArrayList<Integer> printMatrix(int[][] matrix)
5 {
6 ArrayList<Integer> res = new ArrayList<>();
7 int left = 0, right = matrix[0].length - 1, up = 0, bottom = matrix.length - 1;
8 while (left <= right && up <= bottom)
9 {
10 for (int i = left; i <= right; i++)
11 res.add(matrix[up][i]);
12 for (int i = up + 1; i <= bottom - 1; i++)
13 res.add(matrix[i][right]);
14 for (int i = right; i >= left && up != bottom; i--)
15 res.add(matrix[bottom][i]);
16 for (int i = bottom - 1; i >= up + 1 && left != right; i--)
17 res.add(matrix[i][left]);
18 left++;
19 right--;
20 up++;
21 bottom--;
22 }
23 return res;
24 }
25 }
26
27 /* ⭐走不动了就向右拐⭐ */
28 public class JZ29_2
29 {
30 public static boolean[][] vis;
31 public static int m;
32 public static int n;
33
34 public static ArrayList<Integer> printMatrix(int[][] matrix)
35 {
36 m = matrix.length;
37 n = matrix[0].length;
38 vis = new boolean[m][n];
39
40 ArrayList<Integer> res = new ArrayList<>();
41 int cur_x = 0, cur_y = 0, index = 0;
42 int[] ori_x = new int[]{0, 1, 0, -1};
43 int[] ori_y = new int[]{1, 0, -1, 0};
44 while (judge(cur_x, cur_y))
45 {
46 vis[cur_x][cur_y] = true;
47 res.add(matrix[cur_x][cur_y]);
48 if (!judge(cur_x + ori_x[index], cur_y + ori_y[index]))
49 index = (index + 1) % 4;
50 cur_x = cur_x + ori_x[index];
51 cur_y = cur_y + ori_y[index];
52 }
53 return res;
54 }
55
56 public static boolean judge(int cur_x, int cur_y)
57 {
58 return cur_x >= 0 && cur_x < m && cur_y >= 0 && cur_y < n && !vis[cur_x][cur_y];
59 }
60 }
61
62 /* 递归遍历 */
63 public class JZ29_3
64 {
65 public static ArrayList<Integer> res = new ArrayList<>();
66
67 public static ArrayList<Integer> printMatrix(int[][] matrix)
68 {
69 recursion(matrix, 0, matrix[0].length - 1, 0, matrix.length - 1);
70 return res;
71 }
72
73 public static void recursion(int[][] matrix, int left, int right, int up, int bottom)
74 {
75 if (left > right || up > bottom) return;
76
77 for (int i = left; i <= right; i++)
78 res.add(matrix[up][i]);
79 for (int i = up + 1; i <= bottom - 1; i++)
80 res.add(matrix[i][right]);
81 for (int i = right; i >= left && up != bottom; i--)
82 res.add(matrix[bottom][i]);
83 for (int i = bottom - 1; i >= up + 1 && left != right; i--)
84 res.add(matrix[i][left]);
85 recursion(matrix, left + 1, right - 1, up + 1, bottom - 1);
86 }
87
88 public static void main(String[] args)
89 {
90 int[][] martix = SimulateUtils.createMartix(3, 5);
91 ArrayList<Integer> integers = printMatrix(martix);
92 integers.forEach(System.out::println);
93 }
94 }
JZ61 扑克牌顺子
1 /* 滑动窗口 */
2 public class JZ61_1
3 {
4 public static boolean IsContinuous(int[] numbers)
5 {
6 int[] cnt = new int[14];
7 int left = 0, right = 0, need = 5;
8 for (int number : numbers)
9 {
10 cnt[number]++;
11 if (number != 0 && cnt[number] > 1)
12 return false;
13 }
14 while (right < cnt.length)
15 {
16 if (right - left < 5)
17 {
18 right++;
19 if (right < cnt.length && cnt[right] > 0)
20 need--;
21 }
22 else
23 {
24 if (need <= cnt[0])
25 return true;
26 left++;
27 if (cnt[left] > 0)
28 need++;
29 }
30 }
31 return false;
32 }
33 }
34
35 /* maxValue - minValue < 5 */
36 public class JZ61_2
37 {
38 public static boolean IsContinuous(int[] numbers)
39 {
40 int max = Integer.MIN_VALUE, min = Integer.MAX_VALUE;
41 for (int num : numbers)
42 {
43 if (num == 0) continue;
44
45 if (max == num)
46 return false;
47 if (max < num)
48 max = num;
49 if (min == num)
50 return false;
51 if (min > num)
52 min = num;
53 }
54 return max - min <= 4;
55 }
56 }
57
58 /* 统计间隔数 */
59 public class JZ61_3
60 {
61 public static boolean IsContinuous(int[] numbers)
62 {
63 Arrays.sort(numbers);
64 int i = 0, zeros = 0, gap = 0;
65 while (numbers[i] == 0)
66 {
67 zeros++;
68 i++;
69 }
70 for (; i < numbers.length - 1; i++)
71 {
72 if (numbers[i + 1] - numbers[i] == 0) return false;
73 gap = gap + numbers[i + 1] - numbers[i] - 1;
74 }
75 return gap <= zeros;
76 }
77 }
JZ67 把字符串转换成整数(atoi)
1 /* 模拟 */
2 public class JZ67_1
3 {
4 public static int StrToInt(String s)
5 {
6 int idx = 0, res = 0, posFlag = 1;
7 while (idx < s.length() && s.charAt(idx) == ' ')
8 idx++;
9 if (idx == s.length()) return 0;
10 if (s.charAt(idx) == '-')
11 {
12 posFlag = -1;
13 idx++;
14 }
15 else if (s.charAt(idx) == '+') idx++;
16 while (idx < s.length() && Character.isDigit(s.charAt(idx)))
17 {
18 if (posFlag == 1 && (res > Integer.MAX_VALUE / 10 || (res == Integer.MAX_VALUE / 10 && s.charAt(idx) - '0' > Integer.MAX_VALUE % 10)))
19 return Integer.MAX_VALUE;
20 if (posFlag == -1 && (-res < Integer.MIN_VALUE / 10 || (-res == Integer.MIN_VALUE / 10 && s.charAt(idx) - '0' > -(Integer.MIN_VALUE % 10))))
21 return Integer.MIN_VALUE;
22 res = res * 10 + s.charAt(idx) - '0';
23 idx++;
24 }
25 return res * posFlag;
26 }
27 }
JZ20 表示数值的字符串
1 /* 边遍历边判断 */
2 public class JZ20_1
3 {
4 public static boolean isNumeric(String str)
5 {
6 str = str.trim();
7 boolean meetDot = false, meetAlphaE = false, meetNum = false;
8 for (int i = 0; i < str.length(); i++)
9 {
10 char s = str.charAt(i);
11 if (Character.isDigit(s) || s == '.' || Character.toLowerCase(s) == 'e' || s == '+' || s == '-')
12 {
13 if (s == '+' || s == '-')
14 {
15 if (i + 1 == str.length() || str.charAt(i + 1) == '-' || Character.toLowerCase(str.charAt(i + 1)) == 'e')
16 return false;
17 if (i != 0 && Character.toLowerCase(str.charAt(i - 1)) != 'e')
18 return false;
19 }
20 if (s == '.')
21 {
22 if (meetDot || meetAlphaE)
23 return false;
24 else
25 meetDot = true;
26 }
27 if (Character.toLowerCase(s) == 'e')
28 {
29 if (meetAlphaE || !meetNum || i == str.length() - 1)
30 return false;
31 else
32 meetAlphaE = true;
33 }
34 if (Character.isDigit(s))
35 meetNum = true;
36 }
37 else return false;
38 }
39 return meetNum;
40 }
41 }
42
43 /* 以 e 为分界线，分成前后两部分，分别判断 */
44 public class JZ20_2
45 {
46 public static boolean isNumeric(String str)
47 {
48 long count = 0;
49 str = str.toLowerCase().trim();
50 int idxE = str.indexOf('e');
51 if (idxE == -1)
52 {
53 count = str.chars().filter(s -> s == '.').count();
54 if (count > 1 || !judge(str)) return false;
55 }
56 else
57 {
58 String fir = str.substring(0, idxE);
59 count = fir.chars().filter(s -> s == '.').count();
60 if (count > 1 || !judge(fir)) return false;
61
62 String sec = str.substring(idxE + 1);
63 count = sec.chars().filter(s -> s == 'e').count();
64 if (count > 0 || sec.indexOf('.') != -1 || !judge(sec))
65 return false;
66 }
67 return true;
68 }
69
70 public static boolean judge(String str)
71 {
72 int i = 0;
73 boolean meetNum = false;
74 if (str.length() == 0) return false;
75 if (str.charAt(i) == '+' || str.charAt(i) == '-')
76 i++;
77 if (i == str.length()) return false;
78 for (; i < str.length(); i++)
79 {
80 if (Character.isDigit(str.charAt(i)))
81 meetNum = true;
82 else if (str.charAt(i) != '.')
83 return false;
84 }
85 return meetNum;
86 }
87 }
88
89 /* regex */
90 public class JZ20_3
91 {
92 public boolean isNumeric(String str)
93 {
94 String p = "^[+-]?(\\d*\\.\\d+|\\d+(\\.\\d*)?)(?:[eE][+-]?\\d+)?$";
95 return Pattern.matches(p, str.trim());
96 }
97 }
98
99 /* ⭐剑指⭐ */
100 public class JZ20_4
101 {
102 public static int idx = 0;
103
104 public static boolean isNumeric(String str)
105 {
106 StringBuilder s = new StringBuilder(str.trim().toLowerCase());
107 if (s.length() == 0) return false;
108 boolean numeric = scanInteger(s);
109 if (idx < s.length() && s.charAt(idx) == '.')
110 {
111 ++idx;
112 boolean hasNumbers = scanUnsignedInteger(s);
113 numeric = hasNumbers || numeric;
114 }
115 if (idx < s.length() && s.charAt(idx) == 'e')
116 {
117 ++idx;
118 numeric = numeric && scanInteger(s);
119 }
120 return numeric && (idx == s.length());
121
122 }
123
124 public static boolean scanInteger(StringBuilder str)
125 {
126 if (idx >= str.length()) return false;
127 if (str.charAt(idx) == '+' || str.charAt(idx) == '-')
128 ++idx;
129 return scanUnsignedInteger(str);
130 }
131
132 public static boolean scanUnsignedInteger(StringBuilder str)
133 {
134 if (idx >= str.length()) return false;
135 int begin = idx;
136 while (idx < str.length() && str.charAt(idx) >= '0' && str.charAt(idx) <= '9')
137 ++idx;
138 return idx > begin;
139 }
140 }
