Integer Value Problem [duplicate]

This question already has answers here: 开发者_JS百科 Closed 12 years ago.

Possible Duplicate:

How can I pad an int with leading zeros when using cout << operator?

How could I show 01 in an integer?

whenever I convert a string to integer, I always get 1 instead of 01.

How could get a 01 value.

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Since you tagged it as C++, the way to do it with C++'s streams could be the following:

#include <sstream>
#include <iomanip>
#include <iostream>

int main() {    
    int value = 1;
    std::stringstream ss;
    ss.width(2);
    ss << std::setfill('0') << value;

    std::cout << ss.str() << std::endl; // displays '01'
}

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Don't confuse the value that's stored with the way you want it presented.

You can just use:

std::cout << std::setfill('0') << std::setw(2) << 1;

as shown in the following complete program:

#include <iostream>
#include <iomanip>

int main() {
    int x = 1;
    std::cout << std::setfill('0') << std::setw(2) << x << std::endl;
    return 0;
}

which outputs:

01

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The integer type uses all its memory - typically 32 or 64 bits - to cover the largest possible range of distinct integer values it can. It doesn't keep track of any formatting/display information. Consequently, even a 32-bit value can track some 4 billion distinct values, but however they're to be shown on-screen, in files etc. has to be decided by the surrounding code, and is not a property of the integer itself. So, if you have an integer, you can choose the formatting when you display it. There are a variety of ways to do this. The most C++ way is using std::ostream and the <iomanip> header, which includes support for specifying a field width and fill/padding character. For an example, see http://www.cplusplus.com/reference/iostream/manipulators/setw/ and you can follow the "See also" link to setfill. The way inherited from C is...

printf("%02d", n);

...where the first double-quoted string section contains a "format string", in which % introduces a conversion, 0 means to pad and 2 is the width, d means the next decimal/integer value in the list of arguments.

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If you are using printf, use the following formate specifier

printf("%02d\n",myInt);

Here, the 0 after percentage indicates leading zero padding and 2 indicates a field width of 2.

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As an integer, it will always be 1, You can only display 01 when you turn it back into a String for display purposes.

The best way would be to use the printf

printf("%02d", x);

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When displaying the value using a formatter you can write:

%02d

See the C++ reference documentation: http://www.cplusplus.com/reference/clibrary/cstdio/printf/