54. Spiral Matrix
题目
Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.
For example,
Given the following matrix:
[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
You should return [1,2,3,6,9,8,7,4,5].
解析
- 自己亲自写才知道很多细节问题：
- bug1:
y0==y1写成y0=y1赋值语句 - bug2:
for (int row = x1 - 1; row > x0;row--)小标越界row=x1+1 - bug3: 输入为空矩阵判断
if ( matrix.empty())后面判断row<=0||col<=0此时已经出现问题了
class Solution_54 {
public:
void help(vector<vector<int>>& matrix,vector<int> &res, int x0, int y0, int x1, int y1)
{
if (x0==x1&&y0==y1)
{
res.push_back(matrix[x0][y0]);
}else if (x0==x1) //最后一行
{
for (int i = y0; i <= y1;i++)
{
res.push_back(matrix[x0][i]);
}
}else if (y1==y0)
{
for (int i = x0; i <= x1;i++)
{
res.push_back(matrix[i][y0]);
}
}
else
{
for (int col = y0; col <= y1;col++)
{
res.push_back(matrix[x0][col]);
}
for (int row = x0 + 1; row <= x1;row++)
{
res.push_back(matrix[row][y1]);
}
for (int col = y1 - 1; col >= y0;col--)
{
res.push_back(matrix[x1][col]);
}
for (int row = x1 - 1; row > x0;row--)
{
res.push_back(matrix[row][y0]);
}
}
return;
}
vector<int> spiralOrder(vector<vector<int>>& matrix) {
vector<int> res;
if ( matrix.empty()) //
{
return vector<int>(); //res;
}
int row = matrix.size();
int col = matrix[0].size(); //后面判断错误：row <= 0 || col <= 0 ，需要计算row,col调用size()出错，需要在函数开始判断
int x0 = 0, y0 = 0, x1 = row - 1, y1 = col - 1;
while (x0<=x1&&y0<=y1)
{
help(matrix,res, x0, y0, x1, y1);
x0++;
y0++;
x1--;
y1--;
}
return res;
}
};
题目来源
