leetcode-59. Spiral matrix II JS

subject

Code

var generateMatrix = function(n) {
    
    let matrix = []
    for (let i = 0; i < n; i++) {
    
        let arr = new Array(n).fill(0)
        matrix.push(arr)
    }
    let num = 1

    let upper_bound = 0, right_bound = n-1;
    let lower_bound = n-1, left_bound = 0;

    while(num <= n*n) {
    
        //  From left to right 
        if(upper_bound <= lower_bound) {
    
            for (let i = left_bound; i <= right_bound; i++) {
    
                matrix[upper_bound][i] = num++
            }
            upper_bound++
        }

        //  From top to bottom 
        if(right_bound >= left_bound) {
    
            for (let i = upper_bound; i <= lower_bound; i++) {
    
                matrix[i][right_bound] = num++
            }
            right_bound--
        }

        //  From right to left 
        if(lower_bound >= upper_bound) {
    
            for (let i = right_bound; i >= left_bound; i--) {
    
                matrix[lower_bound][i] = num++
            }
            lower_bound--
        }

        //  From bottom to top 
        if(left_bound <= right_bound) {
    
            for (let i = lower_bound; i >= upper_bound; i--) {
    
                matrix[i][left_bound] = num++
            }
            left_bound++
        }
    }

    return matrix
};

Reference material

• Fancy traversal skills of two-dimensional array