[LeetCode]Spiral Matrix II

最新推荐文章于 2019-05-14 09:57:51 发布

原创最新推荐文章于 2019-05-14 09:57:51 发布 · 824 阅读

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本文详细介绍了使用C++语言生成矩阵的方法，包括组件完成时的观察机制，以及从左到右、从上到下、从右到左、从下到上的遍历策略。

class Solution {
//key observe: when each component is done, its beginX,endX or beginY,endX will change
public:
	vector<vector<int> > generateMatrix(int n) {
		
		if(0 == n) return vector<vector<int> >();
		vector<vector<int> >  result(n, vector<int>(n));
		int beginX = 0, endX = n-1;
		int beginY = 0, endY = n-1;
		
		int cur = 1;
		int nSquare = n*n;
		while (true) {
			// From left to right
			for (int i = beginX; i <= endX; ++i)
				result[beginY][i] = cur++;
			if (++beginY > endY) break;
			// From top down
			for (int i = beginY; i <= endY; ++i)
				result[i][endX] = cur++;
			if (beginX > --endX) break;
			// From right to left
			for (int i = endX; i >= beginX; --i)
				result[endY][i] = cur++;
			if (beginY > --endY) break;
			// From bottom up
			for (int i = endY; i >= beginY; --i)
				result[i][beginX] = cur++;
			if (++beginX > endX) break;
		}
		return result;
	}
};

second time

class Solution {
public:
    vector<vector<int> > generateMatrix(int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int start = 0;
        int end = n-1;
        vector<vector<int> > matrix(n, vector<int>(n, 0));
        int curNum = 1;
        while(start <= end)
        {
            //up
            for(int i = start; i <= end; ++i) matrix[start][i] = curNum++;
            //right
            for(int i = start+1; i <= end-1; ++i) matrix[i][end] = curNum++;
            //bottom
            if(start != end)
            for(int i = end; i >= start; --i) matrix[end][i] = curNum++;
            //left
            for(int i = end-1; i >= start+1; --i) matrix[i][start] = curNum++;
            
            start++;
            end--;
        }
        
        return matrix;
    }
};