<h1 style="margin: 0px 0px 0.5em; padding: 0px; border: 0px; font-family: 'Droid Sans', Verdana, 'Microsoft YaHei', Tahoma, sans-serif; font-size: 3em; font-weight: normal; line-height: 1em; vertical-align: baseline; color: rgb(17, 17, 17); background-color: rgb(250, 250, 250);">1001. 害死人不偿命的(3n+1)猜想 (15)</h1><div id="problemInfo" class="rfloat" style="margin: 0px; padding: 2px; border: 1px solid rgb(221, 221, 221); font-family: 'Droid Sans', Verdana, 'Microsoft YaHei', Tahoma, sans-serif; line-height: 18px; vertical-align: baseline; float: right; text-align: center; color: rgb(51, 51, 51); background-color: rgb(250, 250, 250);"><div class="limit" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><div class="key" style="margin: 0px; padding: 0px 20px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; background-color: rgb(221, 221, 221);">时间限制</div><div class="value" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;">400 ms
</div></div><div class="limit" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><div class="key" style="margin: 0px; padding: 0px 20px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; background-color: rgb(221, 221, 221);">内存限制</div><div class="value" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;">65536 kB
</div></div><div class="limit" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><div class="key" style="margin: 0px; padding: 0px 20px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; background-color: rgb(221, 221, 221);">代码长度限制</div><div class="value" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;">8000 B
</div></div><div class="checker" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><div class="key" style="margin: 0px; padding: 0px 20px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; background-color: rgb(221, 221, 221);">判题程序</div><div class="value" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><span title="纯文本对比" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;">Standard</span></div></div><div class="key" style="margin: 0px; padding: 0px 20px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline; background-color: rgb(221, 221, 221);">作者</div><div class="value" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;">CHEN, Yue
</div></div><div id="problemContent" style="margin: 0px; padding: 0px; border: 0px; font-family: 'Droid Sans', Verdana, 'Microsoft YaHei', Tahoma, sans-serif; line-height: 18px; vertical-align: baseline; color: rgb(51, 51, 51); background-color: rgb(250, 250, 250);"><p style="margin-top: 0px; margin-bottom: 1.5em; padding-top: 0px; padding-bottom: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;">卡拉兹(Callatz)猜想：<span style="font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit;">对任何一个自然数n，如果它是偶数，那么把它砍掉一半；如果它是奇数，那么把(3n+1)砍掉一半。这样一直反复砍下去，最后一定在某一步得到n=1。卡拉兹在1950年的世界数学家大会上公布了这个猜想，传说当时耶鲁大学师生齐动员，拼命想证明这个貌似很傻很天真的命题，结果闹得学生们无心学业，一心只证(3n+1)，以至于有人说这是一个阴谋，卡拉兹是在蓄意延缓美国数学界教学与科研的进展……</span></p><p style="margin-top: 0px; margin-bottom: 1.5em; padding-top: 0px; padding-bottom: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;">我们今天的题目不是证明卡拉兹猜想，而是对给定的任一不超过1000的正整数n，简单地数一下，需要多少步（砍几下）才能得到n=1？</p><p style="margin-top: 0px; margin-bottom: 1.5em; padding-top: 0px; padding-bottom: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><strong>输入格式：</strong>每个测试输入包含1个测试用例，即给出自然数n的值。</p><p style="margin-top: 0px; margin-bottom: 1.5em; padding-top: 0px; padding-bottom: 0px; border: 0px; font-family: inherit;font-size:undefined; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; vertical-align: baseline;"><strong>输出格式：</strong>输出从n计算到1需要的步数。</p><strong>输入样例：</strong><pre style="margin-top: 1.5em; margin-bottom: 1.5em; padding: 0px; border: 0px; font-family: 'Droid Sans Mono', Consolas, 'Courier New', monospace; font-size: 1em; line-height: 1.5; vertical-align: baseline; overflow: auto;">3

5

<span style="font-family: Arial, Helvetica, sans-serif;"><span style="font-family: Arial, Helvetica, sans-serif;">#include<stdio.h></span></span>

int main(void)
{
int n,step=0;

scanf("%d",&n);

if(n==1)
printf("%d",step);
else
{
while(n!=1)
{
if(n%2==0)
n=n/2;
else
n=(3*n+1)/2;
step++;
}
printf("%d",step);
}

return 0;
}

</pre><pre name="code" class="plain">

遇到的问题：

while和do-while的使用方法区别

都是循环语句..

对于第一次循环
while是先判断再执行
int i=10;
while(i<10){
System.err.println(i)
i++;
}
结果是什么都不打印,最终i的值为10

do-while是先执行,再判断
int i=10;
do{
System.err.println(i)
i++;
}while(i<10)
打印的也是10,最终i=11

两者的区别在于第一圈循环时,while是先判断循环条件,再循环.所以第一个程序什么都不打印.而do-while则是先执行后判断.所以,第二个程序先打印10,然后i++然后跳出循环..