LeetCode59 Spiral Matrix II

题目：

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: （Medium）

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

分析：

跟 Sprial Matrix I处理方式一样，先建立好n * n的数组，然后按照顺时针顺序填入数字即可。

代码：

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> result(n, vector<int>(n,0));
        int rowBegin = 0, rowEnd = n - 1, colBegin = 0, colEnd = n - 1;
        int count = 1;
        while (rowBegin <= rowEnd && colBegin <= colEnd) {
            for (int i = colBegin; i <= colEnd; ++i ) {
                result[rowBegin][i] = count;
                count++;
            }
            rowBegin++;
            if (rowBegin > rowEnd) {
                break;
            }
            for (int i = rowBegin; i <= rowEnd; ++i) {
                result[i][colEnd] = count;
                count++;
            }
            colEnd--;
            if (colBegin > colEnd) {
                break;
            }
            for (int i = colEnd; i >= colBegin; --i) {
                result[rowEnd][i] = count;
                count++;
            }
            rowEnd--;
            if (rowBegin > rowEnd) {
                break;
            }
            for (int i = rowEnd; i>= rowBegin; --i) {
                result[i][colBegin] = count;
                count++;
            }
            colBegin++;
        }
        return result;
    }
};