Spiral Matrix II 题解

题目来源：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 ] ]

解题思路：

跟 spiral-matrix一样。

    vector<vector<int> > generateMatrix(int n)
    {
        if(n == 0) return vector<vector<int> >();
        vector<vector<int> > matrix(n, vector<int>(n, 0));
        int rowindex = 0;
        int columeindex = n-1;
        int row = n, colume = n;
        int index = 1;
        int size = n * n;
        while(true)
        {
            int toleft_start = rowindex;
            int toleft_end = columeindex;
            int todown_start = rowindex + 1;
            int todown_end = row - rowindex - 1;

            for(int i = toleft_start; i <= toleft_end; i++)
                matrix[rowindex][i] = index++;
            if(index == size+1)
                break;
            for(int i = todown_start; i <= todown_end; i++)
                matrix[i][columeindex] = index++;
            if(index == size+1)
                break;
            for(int i = toleft_end-1; i>= toleft_start; i--)
                matrix[row - rowindex - 1][i] = index++;
            if(index == size+1)
                break;
            for(int i = todown_end-1; i >= todown_start; i--)
                matrix[i][colume-columeindex-1] = index++;
            if(index == size+1)
                break;
            rowindex++;
            columeindex--;
        }
        return move(matrix);
    }