螺旋矩陣

題目大意

　　給定一個m*n的矩陣，輸入全部元素的螺旋順序。

解題思路

　　使用計算輸出的方法，先處理上面一行，再處理右邊一列，再處理下面一行，再處理左邊一列，一直這樣操做，直到全部的元素都處理完。

代碼實現

算法實現類

import java.util.ArrayList;
import java.util.List;

public class Solution {

    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> result = new ArrayList<>(50);

        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return result;
        }

        // 只有一行的狀況
        if (matrix.length == 1) {
            for (int i : matrix[0]) {
                result.add(i);
            }

            return result;
        }

        // 只有一列的狀況
        if (matrix[0].length == 1) {
            for (int i = 0; i < matrix.length; i++) {
                result.add(matrix[i][0]);
            }

            return result;
        }

        // 計算有多少圈
        int row = matrix.length;
        int col = matrix[0].length;
        int cycle = row < col ? row : col;
        cycle = (cycle + 1) / 2;

        int round = 0; // 記錄當前是第幾圈
        int left = 0;
        int right = matrix[0].length - 1;
        int top = 0;
        int down = matrix.length - 1;
        int total = col*row;
        int count = 0;
        while (round < cycle) {

            // 上面一行
            for (int i = left; i <= right && count < total; i++) {
                count++;
                result.add(matrix[round][i]);
            }
            top++; //

            // 右邊一列
            for (int i = top; i <= down && count < total; i++) {
                count++;
                result.add(matrix[i][col - round - 1]);
            }
            right--;

            // 底下一行
            for (int i = right; i >= left && count < total; i--) {
                count++;
                result.add(matrix[row - round - 1][i]);

            }
            down--;

            // 左邊一列
            for (int i = down; i >= top && count < total; i--) {
                count++;
                result.add(matrix[i][round]);
            }
            left++;

            round++;
        }

        return result;
    }
}

 

螺旋矩陣是指一個呈螺旋狀的矩陣，它的數字由第一行開始到右邊不斷變大，向下變大，
　　向左變大，向上變大，如此循環。

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118

import java.util.Scanner;   public class mysnakematrix {     private int n; //     private int a[][]; // 聲明一個矩陣     private int value = 1;// 矩陣裏數字的值       public mysnakematrix(int i) {         this.n = i;         a = new int[n][n];     }       // 計算第m層左上角的數字     private int getcorner(int m) {         int corner = 1;         int o = n - 1;         for (int i = 0; i < m - 1; ++i) {             corner += 4 * o;             o = o - 2;         }         return corner;     }       // 生成矩陣的每一層的每一邊的數     // s表示4個方向，分別取值1,2,3,4，表示4個不一樣的方向。     // o表示這條邊的起始值。     // x表示第m層每條邊的數字個數     private void side(int s, int o, int x, int m) {         int i = 0;         int j = 0;         switch (s) {         case 1:             i = m - 1;             j = m - 1;             for (int k = 0; k < x; ++k) {                 a[i][j + k] = value;                 ++value;             }               break;         case 2:             i = m - 1;             j = m - 1 + x;             for (int k = 0; k < x; ++k) {                 a[i + k][j] = value;                 ++value;             }             break;         case 3:             i = m - 1 + x;             j = m - 1 + x;             for (int k = 0; k < x; ++k) {                 a[i][j - k] = value;                 ++value;             }             break;         case 4:             i = m - 1 + x;             j = m - 1;             for (int k = 0; k < x; ++k) {                 a[i - k][j] = value;                 ++value;             }             break;         }     }       // 生成蛇形矩陣的第m層     private void shell(int m)// m表示第m層     {         int x = n - 1 - (m - 1) * 2; // x表示第m層每條邊的數字個數         int o = getcorner(m);         int o1 = o;         int o2 = o1 + x;         int o3 = o2 + x;         int o4 = o3 + x;         // System.out.println(o4);           side(1, o, x, m);         side(2, o, x, m);         side(3, o, x, m);         side(4, o, x, m);     }       // 生成蛇形矩陣     public void snakeMatrix() {         int m = (n + 1) / 2;// 計算一共有多少層         for (int i = 1; i <= m; ++i) {               shell(i);         }         if (n % 2 == 1) {             a[n / 2][n / 2] = n * n;         }       }       // 打印矩陣     public void print() {         for (int i = 0; i < n; ++i) {             for (int j = 0; j < n; ++j) {                 if (a[i][j] < 10) {                     System.out.print(a[i][j] + "  ");                 } else {                     System.out.print(a[i][j] + " ");                 }               }             System.out.println();         }     }       public static void main(String args[]) {         mysnakematrix my = new mysnakematrix(new Scanner(System.in).nextInt());  //利用Scanner獲取控制檯輸入         my.snakeMatrix();         my.print();     } }