剑指offer:顺时针打印矩阵


问题描述

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。

解题思路

以四个变量up,down,right,left表示当前输出情况,一旦up>down,left>right则表示已输出完。

c++代码

class Solution {
public:
    vector printMatrix(vector > matrix) {
        vector ans;
        int up = 0, left = 0;
        int down = matrix.size()-1;
        int right = matrix[0].size()-1;


        while(true){
            for(int i = left; i <= right; i++)
                ans.push_back(matrix[up][i]);
            up++;
            if(up > down)  break;

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

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

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

    }
};

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