字符串转整型

来源于http://topic.csdn.net/t/20051109/12/4381609.html#上的讨论，结果是

  1 #include "stdafx.h"
  2
  3
  4
  5 namespace{
  6     using std::vector;
  7     vector<vector<int> > matrix(6,vector<int>(9));
  8 }
  9
10 namespace MyTest{
11
12     using std::string;
13     int StrToInt(const string& srcStr){
14         string::size_type result=srcStr.find('.');
15         int bitSize;//位数
16         int sum=0;
17         if (result==string::npos){
18             string::size_type bitSize=srcStr.size();
19             string::size_type j=bitSize-1;
20             for(string::size_type i=0;i<bitSize;i++){
21                 sum+=(srcStr[i]-'0')*
22                     (static_cast<int>(pow(static_cast<double>(10),static_cast<double>(j--))));
23             }
24         }else{
25             //if (srcStr[result+1]<'5'){
26             string::size_type j=bitSize=result-1;
27             for(string::size_type i=0;i<bitSize;i++){
28                 sum+=(srcStr[i]-'0')*
29                     (static_cast<int>(pow(static_cast<double>(10),static_cast<double>(j--))));
30             }
31                 if (srcStr[result+1]<'5')
32                     sum+=(srcStr[bitSize]-'0');//四舍
33                 else
34                     sum+=((srcStr[bitSize]-'0')+1);//五入
35             }
36         return sum;
37     }
38 }
39
40 namespace MyTest{
41     int StrToIntGood(char* str){
42         int sum=0;
43         while(*str!='\0'){
44             sum=sum*10+static_cast<int>(*str-'0');
45             str++;
46         }
47
48         return sum;
49     }
50 }
51
52 namespace MyTest{
53     using std::string;
54     using std::vector;
55     //typedef vector<int>::size_type s_t;
56     int StrToBetter( const string& srcStr){
57
58         //开辟动态数组作为索引
59         size_t stringSize=srcStr.size();
60         //size_t row=stringSize-1;
61         //size_t col=9;
62         //size_t t=1;
63         /*
64         vector<vector<int> > matrix(row,vector<int>(col));
65         for (size_t i=0;i<row;++i){
66             t=t*10;
67             for (size_t j=0;j<col;j++){
68                 matrix[i][j]=t*(j+1);
69             }
70         }
71         */
72         int sum=0;
73         for (size_t i=0;i<stringSize-1;++i){
74             size_t number=srcStr[i]-'0';
75             sum+=::matrix[stringSize-2-i][number-1];
76
77         }
78         sum+=srcStr[stringSize-1]-'0';
79         return sum;
80     }
81 }
82
83 using MyTest::StrToInt;
84 using MyTest::StrToIntGood;
85 using MyTest::StrToBetter;
86 using std::string;
87 using std::cout;
88 using std::endl;
89
90 int _tmain(int argc, _TCHAR* argv[])
91 {
92
93     clock_t now;
94     {
95         int n;
96         now=clock();
97         for(size_t i=0;i<100000;i++)
98             n=atoi("124565");
99         now=clock()-now;
100         cout<<"atoi"<<" "<<n+1<<"time:"<<now<<endl;
101     }
102     {
103
104         int n;
105         now=clock();
106         for(size_t i=0;i<100000;i++)
107             n=StrToInt("124565");
108         now=clock()-now;
109         cout<<"StrToInt"<<" "<<n+1<<"time:"<<now<<endl;
110         //cout<<n+1<<endl;
111         //n=StrToInt("1245.23");
112         //cout<<n+1<<endl;
113         //n=StrToInt("1245.63");
114         //cout<<n+1<<endl;
115     }
116     {
117         char*str=const_cast<char*>("124565");
118         now=clock();
119         int n;
120         for(size_t i=0;i<100000;i++)
121              n=StrToIntGood(str);
122         now=clock()-now;
123         cout<<"StrToIntGood"<<" "<<n+1<<"time:"<<now<<endl;
124     }
125
126     {
127         string stringSize("124565");
128         size_t row=stringSize.size()-1;
129         size_t col=9;
130         int t=1;
131
132         //vector<vector<int> > matrix(row,vector<int>(col));
133         for (size_t i=0;i<row;++i){
134             t=t*10;
135             for (size_t j=0;j<col;j++){
136                 ::matrix[i][j]=t*(j+1);
137             }
138         }
139
140
141         int n;
142         string s("124565");
143         now=clock();
144         for(size_t i=0;i<100000;i++)
145              n=StrToBetter(s);
146         now=clock()-now;
147         cout<<"StrToBetter"<<" "<<n+1<<"time:"<<now<<endl;
148
149     }
150
151     return 0;
152
153 }

posted on 2008-12-22 17:49 风荷小筑阅读(495) 评论(0) 收藏举报