<Prove safety offer> 17 title

topic:

An input matrix, each according to a number from the outside in order to print out sequentially clockwise

Ideas:

The print circle divided into four steps: The first step in printing a line from left to right, top to bottom print one line second step, third step is to print a line from right to left, the fourth step from the bottom line is printed, each The step start coordinate and end coordinate can be printed out by a line or a loop.

There may degenerate into the last lap only one line, and only one, or even only a number, such as print circle no longer needs four steps.

Analyze the prerequisites for each step of printing. The first step is always necessary to print around at least one step. If only one line, then it is not the second step.

The second step is to print a prerequisite for termination line number> starting line number

A third step of printing the proviso that terminating line number> starting line number && termination column number> starting column number

Termination condition is the termination of the fourth step the printing line number than the starting row number is at least 2, while the termination column number> starting column number

Code:

public  class Seventeenth { 

    public  static  void printMatrix ( int [] [] Numbers) {
         IF (Numbers == null ) {
             return ; 
        } 
        // rows start 
        int X = 0 ;
         // record start column 
        int Y = 0 ; 

        // the line number is the largest (numbers.length -. 1) / 2
         // column number is the largest (numbers [0] .length -1) / 2 
        the while (* 2 X <Y numbers.length && * 2 <numbers [0 ] .length) { 
            printMatrixInCircle (Numbers, X, Y); 
            X ++ ;
            Y ++ ; 
        } 
    } 

    public  static  void printMatrixInCircle ( int [] [] Numbers, int X, int Y) {
         int rows = numbers.length;
         int cols = Numbers [0 ] .length; 

        // output the top row 
        for ( int I = Y; I <cols = - Y -. 1; I ++ ) { 
            System.out.println (Numbers [X] [I] + "" ); 
        } 

        // output rightmost column of the loop height of at least 2
         // rows - X -1 represents the row number of the lowermost ring that row 
        IF (rows - X -. 1>X) {
             for ( int I = X +. 1; I <= rows - X -. 1; I ++ ) { 
                System.out.println (Numbers [I] [cols - Y -1] + "" ); 
            } 
        } 

        // loop height and width of the ring is at least 2, at least until the output is below the line 2
         // cols -. 1 - Y denotes a column number of the ring and the rightmost column 
        IF (rows - X -. 1> X && cols - . 1 - Y> Y) {
             for ( int I = cols - Y - 2; I> = Y; I - ) { 
                System.out.println (Numbers [rows -. 1 - X] [I] + "" ); 
            } 
        } 

        // width of the ring height of the ring is at least 2 and 3 will be at least that output leftmost column
         //the line number of the line 1 represents a ring of the lowermost rows - - X 
        IF (cols - 1 - Y> Y && rows - 1 - X> X + 1 ) {
             // the left of the row in the first and last has been output 
            for ( int I = rows -. 1 - X -. 1; I> = X +. 1; I - ) { 
                System.out.println (Numbers [I] [Y] + "" ); 
            } 
        } 
    } 

    public  static  void main (String [] args) {
         int [] [] ARR = { 
                { l, 2,3 }, 
                { 4,5,6 }, 
                { 7,8,9 }  
        };
        printMatrix (ARR);
    }
}