Spiral Matrix II

原创于 2014-05-02 14:22:03 发布 · 336 阅读

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本文介绍了一个使用C++实现的螺旋矩阵生成算法。该算法接受一个整数n作为输入，并生成一个n×n的矩阵，矩阵元素按螺旋顺序从1到n²填充。通过控制四个边界并逐层向内循环填充元素，实现了螺旋式的填充方式。

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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:

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

class Solution {
public:
	vector<vector<int> > generateMatrix(int n) {
		vector<vector<int>> a(n, vector<int>(n));
		int x1 = 0, x2 = n - 1, y1 = 0, y2 = n - 1;
		int k = 1;
		while (x1 <= x2 && y1 <= y2) {
			for(int j = y1; j <= y2; j++)
				a[x1][j] = k++;
			for (int i = x1 + 1; i <= x2; i++)
				a[i][y2] = k++;
			if (x2 != x1) {
				for (int j = y2 - 1; j >= y1; j--)
					a[x2][j] = k++;
			}
			if (y2 != y1) {
				for (int i = x2 - 1; i >= x1 + 1; i--)
					a[i][y1] = k++;
			}
			x1++, y1++, x2--, y2--;
		}
		return a;
	}
};