博客

一、自己的写法

        for(int i=10;i<99;i++){
            for(int j=i;j<99;j++){
                int a = i*j;
                if(a<1000||a>9999)
                    continue;
                String _a = String.valueOf(a);
                String str = _a.substring(2,3);
                if(!str.equals("00")){
                    String _i = String.valueOf(i);
                    String _j = String.valueOf(j);
                    if(_a.indexOf(_i.substring(0,1))!=-1){
                        _a = _a.substring(0,_a.indexOf(_i.substring(0,1))) + _a.substring(_a.indexOf(_i.substring(0,1))+1);
                    }else continue;
                    if(_a.indexOf(_i.substring(1,2))!=-1){
                        _a = _a.substring(0,_a.indexOf(_i.substring(1,2))) +  _a.substring(_a.indexOf(_i.substring(1,2))+1);
                    }else continue;
                    if(_a.indexOf(_j.substring(0,1))!=-1){
                        _a = _a.substring(0,_a.indexOf(_j.substring(0,1))) + _a.substring(_a.indexOf(_j.substring(0,1))+1);
                    }else continue;
                    if(_a.indexOf(_j.substring(1,2))!=-1){
                        _a = _a.substring(0,_a.indexOf(_j.substring(1,2))) + _a.substring(_a.indexOf(_j.substring(1,2))+1);
                    }else continue;
                    if(_a.length()==0){
                        System.out.println(a +"="+i+"*"+j);
                    }
                }
            }
        }

二、巧用取余来得到各个位的数字

        for(int i=1000;i<10000;i++){
            if(i%100==0) continue;
            int a = i/1000; //千位
            int b = i%1000/100; //百位
            int c = i%100/10; //十位
            int d = i%10; //个位

            if((a*10+b)*(c*10+d)==i){
                System.out.println(i+"="+(a*10+b)+"*"+(c*10+d));
            }else if((a*10+b)*(d*10+c)==i){
                System.out.println(i+"="+(a*10+b)+"*"+(d*10+c));
            }else if((b*10+a)*(c*10+d)==i){
                System.out.println(i+"="+(b*10+a)+"*"+(c*10+d));
            }else if((b*10+a)*(d*10+c)==i){
                System.out.println(i+"="+(b*10+a)+"*"+(d*10+c));
            }else if((a*10+c)*(b*10+d)==i){
                System.out.println(i+"="+(a*10+c)+"*"+(b*10+d));
            }else if((a*10+c)*(d*10+b)==i){
                System.out.println(i+"="+(a*10+c)+"*"+(d*10+b));
            }else if((c*10+a)*(b*10+d)==i){
                System.out.println(i+"="+(b*10+d)+"*"+(d*10+b));
            }else if((c*10+a)*(d*10+b)==i){
                System.out.println(i+"="+(c*10+a)+"*"+(d*10+b));
            }else if((a*10+d)*(b*10+c)==i){
                System.out.println(i+"="+(a*10+d)+"*"+(b*10+c));
            }else if((a*10+d)*(c*10+b)==i){
                System.out.println(i+"="+(a*10+d)+"*"+(c*10+b));
            }else if((d*10+a)*(b*10+c)==i){
                System.out.println(i+"="+(d*10+a)+"*"+(b*10+c));
            }else if((d*10+a)*(c*10+b)==i){
                System.out.println(i+"="+(d*10+a)+"*"+(c*10+b));
            }

        }