blocks|key|48604|text|atoi将字符串转换为int。在您的系统上，int为32位，其最大值为2147483647。您尝试转换的值不在此范围内，因此atoi的返回值未定义。我想，在这种情况下，您的实现将返回int的最大值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|48605|您可以使用atoll，它返回一个long+long，保证至少为64位。或者，您可以使用stoi/stol/stoll系列中的一个函数，或者它们的unsigned+counterparts，它将以异常的形式给出有关超出范围的值(和无效值)的有用的错误报告。|48606|就我个人而言，我喜欢boost::lexical_cast。尽管它看起来有点笨拙，但它可以在更一般的上下文中使用。您可以在模板中使用它，只需转发类型参数，而不必进行专门化|48607|entityMap|0|LINK|mutability|MUTABLE|url|http://en.cppreference.com/w/cpp/string/byte/atoi|1|http://en.cppreference.com/w/cpp/string/basic_string/stol|2|http://en.cppreference.com/w/cpp/string/basic_string/stoul|3|http://www.boost.org/doc/libs/1_54_0/doc/html/boost_lexical_cast.html^0|0|4|B|3|M|3|1Q|4|2J|3|0|5|5|17|F|5|5|0|17|F|1|20|L|2|0|A|J|A|J|3|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|18|8|@$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]]|D|@$9|1D|A|1E|1|1F]|$9|1G|A|1H|1|1I]|$9|1J|A|1K|1|1L]]|E|$]]|$1|H|3|I|5|6|7|1M|8|@$9|1N|A|1O|B|C]]|D|@$9|1P|A|1Q|1|1R]]|E|$]]|$1|J|3|-4|5|6|7|1S|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]|R|$5|M|N|O|E|$P|S]]|T|$5|M|N|O|E|$P|U]]|V|$5|M|N|O|E|$P|W]]]]

<code>atoi</code> converts a string to an <code>int</code>. On your system, an <code>int</code> is 32 bits, and its max value is 2147483647. The value you are trying to convert falls outside this range, so the return value of <code>atoi</code> is undefined. Your implementation, I guess, returns the max value of an <code>int</code> in this case.

You could instead use <a href="http://en.cppreference.com/w/cpp/string/byte/atoi"><code>atoll</code></a>, which returns a long long, which is guaranteed to be at least 64 bits. Or you could use a function from the <a href="http://en.cppreference.com/w/cpp/string/basic_string/stol"><code>stoi/stol/stoll</code></a> family, or their <a href="http://en.cppreference.com/w/cpp/string/basic_string/stoul">unsigned counterparts</a>, which will actually give useful error reports on out of range values (and invalid values) in the form of exceptions.

Personally, I like <a href="http://www.boost.org/doc/libs/1_54_0/doc/html/boost_lexical_cast.html"><code>boost::lexical_cast</code></a>. Even though it appears a bit cumbersome, it can be used in a more general context. You can use it in templates and just forward the type argument instead of having to have specializations

blocks|key|48669|text|atoi返回一个带符号的整数，它在您的平台上的最大值是2%5E31-1。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|48670|您将结果赋给什么并不重要，它将由返回类型绑定。|48671|C%2B%2B+streams可以读取无符号整数。|48672|std::istringstream+reader(sThis);
unsigned+int+val;
reader+>>+val;|code-block|syntax|javascript|48673|entityMap^0|R|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|U|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|V|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

atoi returns a signed int, which on your platform has a max value of <code>2^31-1</code>.

It doesn't matter what you're assigning that result to, it will be bounded by the return type.

C++ streams can read unsigned ints.

<pre><code>std::istringstream reader(sThis);
unsigned int val;
reader &gt;&gt; val;
</code></pre>

blocks|key|48723|text|相反，您应该使用<cstdlib>中的std::strtoul，它是为无符号数字设计的，具有更大的范围，并且更好地报告错误。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|48724|如果您希望使用std::string作为输入，使用std::stoul进行异常处理。简短、高效的实现如下所示：|48725|#include+<string>
#include+<stdexcept>
inline+unsigned+int+stoui(const+std::string&+s)
{
++++unsigned+long+lresult+=+stoul(s,+0,+10);
++++unsigned+int+result+=+lresult;
++++if+(result+!=+lresult)+throw+std::out_of_range();
++++return+result;
}|code-block|syntax|javascript|48726|这将比istringstream快得多，区域性不变(因此在不寻常的语言环境中运行时不会有意外的行为变化)，完全可移植，并且使用第三个参数，您可以支持不同的数基，甚至执行0x和0前缀的检测。|48727|但是unsigned+int不一定足够大来容纳您的值，所以使用unsigned+long，这样就不需要上面的包装器了。|48728|entityMap^0|8|9|J|C|0|7|B|P|A|0|0|3|D|2C|2|2F|1|0|2|C|V|D|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|12|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]|$9|18|A|19|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|R|$]]

You should instead use <code>std::strtoul</code>, found in <code>&lt;cstdlib&gt;</code>, which is designed for unsigned numbers, has a larger range, and reports errors better.

If you want to use <code>std::string</code> for input and exceptions for error handling, use <code>std::stoul</code>. A short, highly efficient implementation would be as follows:

<pre><code>#include &lt;string&gt;
#include &lt;stdexcept&gt;
inline unsigned int stoui(const std::string&amp; s)
{
 unsigned long lresult = stoul(s, 0, 10);
 unsigned int result = lresult;
 if (result != lresult) throw std::out_of_range();
 return result;
}
</code></pre>

This will be much faster than <code>istringstream</code>, culture-invariant (so no unexpected changes to behavior when run in an unusual locale), completely portable, and using the third argument, you can support different numeric bases or even perform detection of <code>0x</code> and <code>0</code> prefixes.

But <code>unsigned int</code> isn't necessarily big enough to hold your value, so use <code>unsigned long</code>, and then you won't need the above wrapper.

blocks|key|48764|text|无符号整数通常是C%2B%2B中的32位值，最大值为4,294,967,295。因此，2,154,710,440可以表示为无符号整数。但是，atoi会转换为有符号的整数，并且最大值为2,147,483,647+-因此字符串溢出了值范围，这就是为什么你的答案是不正确的。您可以使用atoll将字符串转换为至少64位的长字符串。在C%2B%2B中，整数大小依赖于编译器。通常更好的做法是包含头文件stdint.h，然后使用uint32_t或uint64_t等，这样您就可以知道要处理的大小。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|48765|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

An unsigned int is often a 32 bit value in C++ which has a maximum of 4,294,967,295.
2,154,710,440 can therefore be represented as an unsigned int. However, atoi converts to an int which is signed and has a maximum value of 2,147,483,647 - so you string overflows the value range whichis why your answer is incorrect. You could use atoll which converts your string to a long long which will be at least 64 bits. 
Integer sizes are compiler dependent in C++. It is often better to include the header file stdint.h and then use uint32_t or uint64_t and so on, so that you know the size you are dealing with.

blocks|key|265438|text|您可以使用atol将字符串转换为long+int。要阅读更多内容，请参阅man+atol+in+Linux。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|265439|原型|265440|#include+<stdlib.h>
long+atol(const+char+*nptr);|code-block|syntax|javascript|265441|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

you can use atol which convert string to long int .
To read more see the man atol in Linux.

the prototype 

<pre><code>#include &lt;stdlib.h&gt;
long atol(const char *nptr);
</code></pre>

blocks|key|48816|text|不幸的是，C%2B%2B没有用于解析unsigned+int的嵌入式实现，这真的很奇怪。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|48817|这是一个可以帮助你的代码：|48818|#include+<stdint.h>
#include+<sstream>

inline+unsigned+int+stoui(const+std::string&+s)
{
++++std::istringstream+reader(s);
++++unsigned+int+val+=+0;
++++reader+>>+val;
++++return+val;
}

//+This+may+be+not+the+same+as+stoui+on+some+platforms:
inline+uint32_t+stoui32(const+std::string&+s)
{
++++std::istringstream+reader(s);
++++uint32_t+val+=+0;
++++reader+>>+val;
++++return+val;
}|code-block|syntax|javascript|48819|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Unfortunately C++ has no embedded implementation for parsing unsigned int and this is really strange.

Here is a code which can help you:

<pre><code>#include &lt;stdint.h&gt;
#include &lt;sstream&gt;

inline unsigned int stoui(const std::string&amp; s)
{
 std::istringstream reader(s);
 unsigned int val = 0;
 reader &gt;&gt; val;
 return val;
}

// This may be not the same as stoui on some platforms:
inline uint32_t stoui32(const std::string&amp; s)
{
 std::istringstream reader(s);
 uint32_t val = 0;
 reader &gt;&gt; val;
 return val;
}
</code></pre>

blocks|key|48873|text|下面的代码将使用C%2B%2B11对其进行转换：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|48874|std::string+sThis+=+"2154910440";
unsigned+int+iStart+=+static_cast<unsigned+int>(std::stoul(sThis));|code-block|syntax|javascript|48875|std::stoul将返回一个比unsigned+int大的unsigned+long。|offset|length|style|CODE|48876|static_cast会将其转换为正确的类型。|48877|entityMap^0|0|0|0|A|G|C|U|D|0|0|B|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]|$I|V|J|W|K|L]|$I|X|J|Y|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@$I|10|J|11|K|L]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|P|$]]

This code will convert it with C++11:

<pre><code>std::string sThis = "2154910440";
unsigned int iStart = static_cast&lt;unsigned int&gt;(std::stoul(sThis));
</code></pre>

<code>std::stoul</code> will return an <code>unsigned long</code>, which is larger than an <code>unsigned int</code>.

<code>static_cast</code> will convert it to the right type.

I have the following string:

<pre><code>sThis = "2154910440";

unsigned int iStart=atoi(sThis.c_str());
</code></pre>

However the result is

<pre><code>iStart = 2147483647
</code></pre>

Does anybody see my mistake?

Converting string to unsigned int returns the wrong result

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有以下字符串：sThis = "2154910440";unsigned int iStart=atoi(sThis.c_str());然而，结果是iStart = 2147483647有人看到我的错误了吗？

问将string转换为unsigned int会返回错误的结果
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问将string转换为unsigned int会返回错误的结果EN