1: class Program
2: {
3: static void Main(string[] args)
4: {
5: string s = File.ReadAllText(@"e:\test.txt");
6: Program p = new Program();
7: string r6 = p.Replace_1(s, ' ', 'a');
8: string r7 = p.Replace_2(s, " ", "a");
9: string r1=p.ReplaceEmptyChar_1(s, "a");
10: string r2 = p.ReplaceEmptyChar_2(s, "a");
11: string r3 = p.ReplaceEmptyChar_3(s, "a");
12: string r4 = p.ReplaceEmptyChar_4(s, "a");
13: string r5 = p.ReplaceEmptyChar_5(s, 'a');
14: string r8 = p.ReplaceEmptyChar_6(s, 'a');
15: Console.WriteLine(string.Equals(r5, r7));
16: }
17:
18: /// <summary>
19: /// replace empty char with new string
20: /// </summary>
21: /// <param name="s">string to be dealed</param>
22: /// <param name="to_be_replaced">replace with this string</param>
23: /// <returns>new string</returns>
24: public string ReplaceEmptyChar_1(string s,string to_be_replaced)
25: {
26: if (string.IsNullOrEmpty(s) || string.IsNullOrEmpty(to_be_replaced) || to_be_replaced==" ")
27: {
28: return s;
29: }
30:
31: char[] charArray = s.ToCharArray();
32: char[] replaceArray = to_be_replaced.ToCharArray();
33: int replaced_length=to_be_replaced.Length;
34: //get the empty count
35: int emptyCount = 0;
36: for (int i=0;i<charArray.Length;i++)
37: {
38: if (charArray[i] == ' ')
39: {
40: emptyCount++;
41: if (replaced_length==1)
42: {
43: charArray[i] = replaceArray[0];
44: }
45: }
46: }
47:
48:
49: if (emptyCount == 0)
50: {
51: return s;
52: }
53:
54: //no need to resize array and return the new string directly
55: if (replaced_length == 1)
56: {
57: return new string(charArray);
58: }
59:
60: int newSeats = (replaced_length - 1) * emptyCount;
61: int oldSize = charArray.Length;
62: int newSize=oldSize+newSeats;
63: Array.Resize<char>(ref charArray, newSize);
64: for (int i = oldSize - 1; i >= 0; i--)
65: {
66: if (charArray[i] == ' ')
67: {
68: for (int j = 0; j < replaced_length; j++)
69: {
70: charArray[newSize - j - 1] = to_be_replaced[replaced_length - j - 1];
71: }
72: newSize -=replaced_length ;
73: }
74: else
75: {
76: charArray[newSize - 1] = charArray[i];
77: newSize--;
78: }
79: }
80:
81: return new string(charArray);
82: }
83:
84: /// <summary>
85: /// use string builder
86: /// </summary>
87: public string ReplaceEmptyChar_2(string s, string to_be_replaced)
88: {
89: StringBuilder sb=new StringBuilder();
90: foreach(char c in s)
91: {
92: if (c == ' ')
93: {
94: sb.Append(to_be_replaced);
95: }
96: else
97: {
98: sb.Append(c);
99: }
100: }
101: return sb.ToString();
102: }
103:
104: /// <summary>
105: /// use string builder
106: /// </summary>
107: public string ReplaceEmptyChar_3(string s, string to_be_replaced)
108: {
109: StringBuilder sb = new StringBuilder(s.Length*2);
110: foreach (char c in s)
111: {
112: if (c == ' ')
113: {
114: sb.Append(to_be_replaced);
115: }
116: else
117: {
118: sb.Append(c);
119: }
120: }
121: return sb.ToString();
122: }
123:
124: /// <summary>
125: /// use list
126: /// </summary>
127: public string ReplaceEmptyChar_4(string s, string to_be_replaced)
128: {
129: List<char> list = new List<char>(s.Length * 2);
130: foreach (char c in s)
131: {
132: if (c == ' ')
133: {
134: foreach (char c2 in to_be_replaced)
135: {
136: list.Add(c2);
137: }
138: }
139: else
140: {
141: list.Add(c);
142: }
143: }
144: return new string(list.ToArray());
145: }
146:
147: /// <summary>
148: /// unsafe pointer
149: /// </summary>
150: public unsafe string ReplaceEmptyChar_5(string s, char to_be_replaced)
151: {
152: int emptyCount = 0;
153: fixed (char* c = s)
154: {
155: char* cp = c;
156: for (int i = 0; i < s.Length; i++)
157: {
158: if (*cp == ' ')
159: {
160: *cp = to_be_replaced;
161: }
162: cp++;
163: }
164:
165: if (emptyCount == 0)
166: {
167: return s;
168: }
169: return new string(c);
170: }
171:
172: }
173:
174: public string ReplaceEmptyChar_6(string s, char to_be_replaced)
175: {
176: char[] charArray = s.ToCharArray();
177:
178: for (int i = 0; i < charArray.Length; i++)
179: {
180: if (charArray[i] == ' ')
181: {
182: charArray[i] = to_be_replaced;
183: }
184: }
185: return new string(charArray);
186: }
187:
188: /// <summary>
189: /// use string.Replace
190: /// </summary>
191: public string Replace_2(string s, string old, string to_be_replaced)
192: {
193: return s.Replace(old, to_be_replaced);
194: }
195:
196: /// <summary>
197: /// use string.Replace
198: /// </summary>
199: public string Replace_1(string s, char old, char to_be_replaced)
200: {
201: return s.Replace(old, to_be_replaced);
202: }
203:
204: /****
205: 用指定字符串替换空白字符的三个实现比较，发现还是框架自带方法Replace快很多
206: Reflector一下发现Replace实现在COMString.cpp中，native的优势~~~~~
207: 为了更深刻反映native的优势，通过ReplaceEmptyChar_5实现一个unsafe的方法，其中用到指针
208: 该方法只简单做字符替换，而Replace也有一个字符替换的重载，同时实现一个managed版本的字符替换方法ReplaceEmptyChar_6
209: 实现结果标明使用了unsfae的指针之后，性能也有较大提升
210: ****/
211: }
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