顺时针打印矩阵

题目描述

输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字，例如，如果输入如下4 X 4矩阵： 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 则依次打印出数字1,2,3,4,8,12,16,15,14,13,9,5,6,7,11,10.

解法：

class Solution {
public:
    vector<int> printMatrix(vector<vector<int> > matrix) 
    {
        vector<int> res;
        int n = matrix.size(), m = matrix[0].size();
        int up = 0, down = n-1, left = 0, right = m-1;
        while(true)
        {
            for(int i = left; i <= right; ++i) res.push_back(matrix[up][i]);
            if(++up > down) break;

            for(int i = up; i <= down; ++i) res.push_back(matrix[i][right]);
            if(--right < left) break;

            for(int i = right; i >= left; --i) res.push_back(matrix[down][i]);
            if(--down < up) break;

            for(int i = down; i >= up; --i) res.push_back(matrix[i][left]);
            if(++left > right)
                break;     
        }
        return res;
    }
};