力扣 54. 螺旋矩阵

题目描述：

给你一个 m 行 n 列的矩阵 matrix ，请按照 顺时针螺旋顺序 ，返回矩阵中的所有元素。

解析：

1.如果数组为空，则返回空数组
2.定义四个边界及当前方向
3.当左边界小于等于右边界，且上边界小于等于下边界时，执行while循环：
按照右、下、左、上的顺序，依次将路径上的字符添加到结果里
4.while循环结束后，返回结果

Java:

public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> result = new ArrayList();
        if(matrix.length == 0) {
            return result;
        }
        int top = 0;
        int bottom = matrix.length - 1;
        int left = 0;
        int right = matrix[0].length - 1;
        String direction = "right";

        while(left <= right && top <= bottom) {
            if(direction == "right") {
                for(int i = left; i <= right; i++) {
                    result.add(matrix[top][i]);
                }
                top++;
                direction = "down";
            } else if(direction == "down") {
                for(int i = top; i <= bottom; i++) {
                    result.add(matrix[i][right]);
                }
                right--;
                direction = "left";
            } else if(direction == "left") {
                for(int i = right; i >= left ; i--) {
                    result.add(matrix[bottom][i]);
                }
                bottom--;
                direction = "top";
            } else if(direction == "top") {
                for(int i = bottom; i >= top; i--) {
                    result.add(matrix[i][left]);
                }
                left++;
                direction = "right";
            }
        }
        return result;
    }

JavaScript:

var spiralOrder = function(matrix) {
    if(matrix.length === 0) {
        return [];
    }
    let top = 0;
    let bottom = matrix.length - 1;
    let left = 0;
    let right = matrix[0].length - 1;
    let direction = "right";
    let result = [];

    while(left <= right && top <= bottom) {
        if(direction === "right") {
            for(let i = left; i <= right; i++) {
                result.push(matrix[top][i]);
            }
            top++;
            direction = "down";
        } else if(direction === "down") {
            for(let i = top; i <= bottom; i++) {
                result.push(matrix[i][right]);
            }
            right--;
            direction = "left";
        } else if(direction === "left") {
            for(let i = right; i >= left; i--) {
                result.push(matrix[bottom][i]);
            }
            bottom--;
            direction = "top";
        } else if(direction === "top") {
            for(let i = bottom; i >= top; i--) {
                result.push(matrix[i][left]);
            }
            left++;
            direction = "right";
        }
    }
    return result;
};