054.Spiral Matrix

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##Solution 2: accepted

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public static List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> result = new ArrayList<>();
        int m = matrix.length;// rows
        if (m == 0) {
            return result;
        }
        int n = matrix[0].length;// columns
        int topOffset = 0;
        int rightOffset = 0;
        int bottomOffset = 0;
        int leftOffset = 0;
        while (true) {
            // top
            for (int i = leftOffset; i < n - rightOffset; i++) {
                result.add(matrix[topOffset][i]);
            }
            topOffset++;
            if (topOffset + bottomOffset == m) {
                break;
            }
            // right
            for (int i = topOffset; i < m - bottomOffset; i++) {
                result.add(matrix[i][n - 1 - rightOffset]);
            }
            rightOffset++;
            if (leftOffset + rightOffset == n) {
                break;
            }
            // bottom
            for (int i = n - 1 - rightOffset; i >= leftOffset; i--) {
                result.add(matrix[m - 1 - bottomOffset][i]);
            }
            bottomOffset++;
            if (topOffset + bottomOffset == m) {
                break;
            }
            // left
            for (int i = m - 1 - bottomOffset; i >= topOffset; i--) {
                result.add(matrix[i][leftOffset]);
            }
            leftOffset++;
            if (leftOffset + rightOffset == n) {
                break;
            }
        }
        return result;
    }