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59. spiral matrix

admin 11月 13, 2020 0

description

给出两道题，同类型的：
一道是返回顺时针矩阵的列表
一道是生成顺时针矩阵

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
You should return [1,2,3,6,9,8,7,4,5]

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,
Given n = 3,

You should return the following matrix:
[
[ 1, 2, 3 ],
[ 8, 9, 4 ],
[ 7, 6, 5 ]
]

思路与题解

实质上是自走迷宫，大问题化为小问题，每次都是右下左上，当不能走时表示结束

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public List<Integer> (int[][] matrix) {
    List<Integer> arr=new ArrayList<>();
    if(matrix==null||matrix.length==0)return arr;
    int len1s,len2s,len1e,len2e;
    len1s=len2s=0;
    len1e=matrix.length-1;
    len2e=matrix[0].length-1;
    int i,j;
    i=j=0;
    while (true){
        switch (1){
            case 1:
                if(j<=len2e){
                    while (j<=len2e){
                        arr.add(matrix[i][j]);
                        j++;
                    }
                    j--;
                    i++;
                    len1s++;
                }else {
                    return arr;
                }
            case 2:
                if(i<=len1e){
                    while (i<=len1e){
                        arr.add(matrix[i][j]);
                        i++;
                    }
                    i--;
                    j--;
                    len2e--;
                }else {
                    return arr;
                }
            case 3:
                if(j>=len2s){
                    while (j>=len2s){
                        arr.add(matrix[i][j]);
                        j--;
                    }
                    j++;
                    i--;
                    len1e--;
                }else {
                    return arr;
                }
            case 4:
                if(i>=len1s){
                    while (i>=len1s){
                        arr.add(matrix[i][j]);
                        i--;
                    }
                    i++;
                    j++;
                    len2s++;
                }else {
                    return arr;
                }
        }
    }
}
 
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public int[][] generateMatrix(int n) {
    int[][] arr=new int[n][n];
    if(n==0)return arr;
    int num=0;
    int i,j;
    int left,right,on,under;
    i=j=0;
    left=on=0;
    right=under=n-1;
    while (true) {
        if (i <=right) {
            while (i <= right) {
                arr[j][i] = ++num;
                i++;
            }
            i--;
            j++;
            on++;
        }else return arr;
        if (j <= under) {
            while (j<=under){
                arr[j][i]=++num;
                j++;
            }
            j--;
            i--;
            right--;
        }else return arr;
        if(i>=left){
            while (i>=left){
                arr[j][i]=++num;
                i--;
            }
            i++;
            j--;
            under--;
        }else return arr;
        if(j>=on){
            while (j>=on){
                arr[j][i]=++num;
                j--;
            }
            j++;
            i++;
            left++;
        }else return arr;
    }
}
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