为何这个程序输入的三个数据只能是n1<n1<n3才可以比较,否则就不可以比较大小;急

if()管的范围要加上{}，如下：
               if(n1<n2){
               n4=n1;
               n1=n2;
               n2=n4;}
               if(n1<n3){
               n4=n1;
               n1=n3;
               n3=n4;}
               if(n2<n3){
               n4=n2;
               n2=n3;
               n3=n4;}