Realization of common library function atoi,itoa,strcpy,strcmp in C + + __jquery

Realization of C + + Common library function atoi,itoa,strcpy,strcmp

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Implementation of 1 1.//integer conversion into string itoa function

2 #include "stdafx.h"

3 #include <iostream>

4 using namespace Std;

5 void itoatest (int num,char str[])

6 {

7 int sign = Num,i = 0,j = 0;

8 Char temp[11];

9 if (sign<0)//To determine whether it is a negative number

10 {

num =-num;

12};

Do

14 {

Temp[i] = num%10+ ' 0 ';

num/=10;

i++;

}while (num>0);

if (sign<0)

20 {

temp[i++] = '-';

22}

Temp[i] = ' the ';

i--;

while (i>=0)

26 {

STR[J] = Temp[i];

j + +;

i--;

30}

STR[J] = ' the ';

32}

33 2. The implementation of string conversion into integer atoi function

int Atoitest (char s[])

35 {

int i = 0,sum = 0,sign; The number you entered may be preceded by a space or a tab should be judged

Notoginseng while (' ==s[i]| | ' \ t ' ==s[i])

38 {

i++;

40}

Sign = ('-' ==s[i])? -1:1;

if ('-' ==s[i]| | ') + ' ==s[i])

43 {

i++;

45}

while (s[i]!= ' ")

47 {

sum = s[i]-' 0 ' +sum*10;

i++;

50}

Sign*sum;

52}

53

54

55 3.//String Copy function

#include "stdafx.h"

#include <assert.h>

#include <string.h>

#include <iostream>

using namespace Std;

*srcpy Char (char *dest,const char *source)

62 {

An ASSERT ((dest!=null) && (source!=null));

The char *address = dest;

while (*source!= ' ")

66 {

*dest++=*source++;

68}

*dest = ' the ";

return to address;

71}

72

73 4.//to determine if the input is a palindrome string

#include "stdafx.h"

#include <string.h>

#include <iostream>

The using namespace Std;

78//Method one: With the help of array

Ispalindrome-BOOL (char *input)

80 {

Bayi Char s[100];

strcpy (S,input);

Length of int = strlen (input);

The int begin = 0,end = Length-1;

while (Begin<end)

86 {

if (S[begin]==s[end])

88 {

begin++;

end--;

91}

He else

93 {

The break;

95}

96}

if (begin<end)

98 {

return false;

100}

Or else

102 {

The return true;

104}

105}

106//Method two: Use pointers

isPalindrome2 bool (char *input)

108 {

109 if (input==null)

The return false;

+ Char *begin = input;

112 Char *end = Begin+strlen (input)-1;

113 while (begin<end)

114 {

if (*begin++!=*end--)

116 return false;

117}

118 return true;

119}

120

121 int Main (int argc, char* argv[])

122 {

123 Char *s = "1234554321";

124 if (Ispalindrome (s))

125 {

126 cout<< "True" <<endl;

127}

128 Else

129 {

130 cout<< "Fasle" <<endl;

131}

132

if (isPalindrome2 (s))

134 {

135 cout<< "True" <<endl;

136}

137 Else

138 {

139 cout<< "Fasle" <<endl;

140}

Cin.get ();

142

143 return 0;

144}

145

146

147 5.//does not use the library function, writes the function int strcmp (char *source, char *dest), if equal returns 0, otherwise returns-1

148 int strcmp (char *source, char *dest)

149 {

An assert (source!= null && dest!= null);

151 while (*source++==*dest++)

152 {

153 if (*source== ' &&*dest== ')

154 return 0;

155}

156 return-1;

157}

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