[LeetCode][JavaScript]Spiral Matrix II

Spiral Matrix II

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 ]
]

https://leetcode.com/problems/spiral-matrix-ii/

 

 

 

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跟上一题一样的思路：http://www.cnblogs.com/Liok3187/p/4842329.html

每做完一条边，就缩小对应长或宽的范围。

/**
 * @param {number} n
 * @return {number[][]}
 */
var generateMatrix = function(n) {
    var res = [], i , j, count = 1;
    for(i = 0; i < n; i++){
        res[i] = [];
        for(j = 0; j < n; j++){
            res[i].push(0);
        } 
    }
    var heightStart = widthStart = 0, heightEnd = widthEnd = n - 1;
    n = Math.ceil(n / 2);
    while(n--){
        for(i = widthStart; i <= widthEnd; i++){
            res[heightStart][i] = count++;
        }
        heightStart++;
        for(i = heightStart; i <= heightEnd; i++){
            res[i][widthEnd]  = count++;
        }
        widthEnd--;
        for(i = widthEnd; i >= widthStart; i--){
            res[heightEnd][i] = count++;
        }
        heightEnd--;
        for(i = heightEnd; i >= heightStart; i--){
            res[i][widthStart]  = count++;
        }
        widthStart++;
    }
    return res;
};