常用函数

//倒序：int reverse(int n){int sum=0;while(n!=0){    sum=sum+n%10;    n=n/10;    if(n!=0)    sum=sum*10;}return sum;}//三角形判断：int isTriangle(double a,double b,double c) {if(a+b>c&&a+c>b&&b+c>a)return 1;elsereturn 0;}//前n项和：int SumAfterN(int n) {int sum=0,i;for(i=1;i<=n;i++)sum+=i;return sum;}//是否是素数：int isPrime(int n){int i,sign=1;if(n<2)    sign=0;for(i=2;i<=sqrt(n);i++){if(n%i==0){    sign=0;}}return sign;}

</pre><pre code_snippet_id="533898" snippet_file_name="blog_20141126_1_8563484" name="code" class="plain">//计算每个月份分别有几天int mouth(int y,int m){          int day;          switch(m){              case 1:              case 3:              case 5:              case 7:              case 8:              case 10:              case 12:                  day=31;                  break;              case 4:              case 6:              case 9:              case 11:                  day=30;                  break;              case 2:                  if((y%100!=0&&y%4==0)||(y%400)==0)//把||变成了&& ，以及把后面的==0忘记了                       day=29;                  else                      day=28;                  break;              default:                  day=0;          }          return day;      }