ccccccccccccc

请编写函数fun，其功能是：判断t所指字符串中的字母是否由连续递增字母序列组成(字符串长度大于等于2)。例如字符串：uvwxyz满足要求；而字符串：uvxwyz不满足要求。 注意：部分源程序存放在PROG1.C中，请勿改动主函数main和其他函数中的任何内容，仅在函数fun指定的部位填入所编写的若干语句。 试题程序：

<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string">"stdio.h"</span></span>
<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string">"string.h"</span></span>
<span class="hljs-function"><span class="hljs-type">int</span> <span class="hljs-title">fun</span><span class="hljs-params">(<span class="hljs-type">char</span> t[])</span>
</span>{
    <span class="hljs-type">int</span> len = <span class="hljs-built_in">strlen</span>(t);
    <span class="hljs-keyword">for</span>(<span class="hljs-type">int</span> i=<span class="hljs-number">0</span>;i<len<span class="hljs-number">-1</span>;i++)
        <span class="hljs-keyword">if</span> (t[i]+<span class="hljs-number">1</span>!=t[i+<span class="hljs-number">1</span>]){
            <span class="hljs-keyword">return</span> <span class="hljs-number">0</span>;
        }
    <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>;
}

<span class="hljs-function"><span class="hljs-type">void</span> <span class="hljs-title">main</span><span class="hljs-params">()</span>
</span>{
    <span class="hljs-type">char</span> s[<span class="hljs-number">100</span>];
    <span class="hljs-built_in">gets</span>(s);
    <span class="hljs-keyword">if</span> (<span class="hljs-built_in">fun</span>(s))
        <span class="hljs-built_in">printf</span>(<span class="hljs-string">"%s 是由连续递增字母序列组成"</span>,s);
    <span class="hljs-keyword">else</span>
        <span class="hljs-built_in">printf</span>(<span class="hljs-string">"%s 不是由连续递增字母序列组成"</span>,s);
}

<span class="hljs-built_in">int</span> fun(<span class="hljs-built_in">char</span> *<span class="hljs-built_in">str</span>)
{
    <span class="hljs-keyword">for</span>(<span class="hljs-built_in">int</span> i=<span class="hljs-number">1</span>;<span class="hljs-built_in">str</span>[i]!=<span class="hljs-number">0</span>;i++)
    {
        <span class="hljs-keyword">if</span> (<span class="hljs-built_in">str</span>[i] != <span class="hljs-built_in">str</span>[i<span class="hljs-number">-1</span>] + <span class="hljs-number">1</span>)
            <span class="hljs-keyword">return</span> <span class="hljs-number">0</span>;
    }
    <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>;
}