第一種思路：

swift：

 let array1=NSMutableArray.init(array: [1,2,3,4]);
        let array22 = NSMutableArray.init(array: []);
        for index1 in 0 ..<4 {
            let a1=array1[index1];
            for index2  in  0 ..<4 {
                let a2=array1[index2]
                if (a1 as! Int)==(a2 as!  Int) {
                    continue;
                }
                for index3  in  0 ..<4 {
                    let a3=array1[index3]
                    if (a1  as!  Int)==(a3  as!  Int)||(a2  as!  Int)==(a3  as!  Int) {
                        continue;
                    }else{
                        let mid = (a1  as!  Int)*100+(a2  as!  Int)*10+(a3  as!  Int)
                        array22.addObject(mid);
                    }
                }
            }
        }
        print("不重複",array22.count)
        print( array22)
 

第二種思路：

(1).swift

 let array1=NSMutableArray.init(array: [1,2,3,4]);
        let array22 = NSMutableArray.init(array: []);
        for index1  in  0 ..<4 {
            if(index1 != 0){
                let tmp1=array1[index1];
                array1[index1]=array1[0];
                array1[0]=tmp1;
            }
            let a1=array1[0];
            for index2  in  1 ..<4 {
                let a2=array1[index2]
                for index3  in  1 ..<4 {
                    let a3=array1[index3]
                    if ((a2  as!  Int) != (a3  as!  Int)) {
                        let mid = (a1  as!  Int)*100+(a2  as!  Int)*10+(a3  as!  Int)
                        array22.addObject(mid);
                    }
                }
            }
        }
        print("2不重複",array22.count)
        print( array22)
 

(2).java

public staticint getTotal(int index) {
    return index>1 ? index*getTotal(index-1) :1;
}
public staticvoid main(String[] args) {
    String number[]={"1","2","3","4"};
    int total=getTotal(number.length);
    System.out.println("total="+total);
    for(int i=0;i<number.length;i++){
        if(i !=0){
            String tmp1=number[i];
            number[i]=number[0];
            number[0]=tmp1;
        }
        for(int j=1;j<number.length;j++){
            for(int k=1;k<number.length;k++){
                if(j!=k)
                    System.out.println(number[0]+number[j]+number[k]);
            }
        }
    }    
}
 

第三種思路：

總結：