topic
Sword Finger Offer 29. Print matrix clockwise
Enter a matrix and print out each number in clockwise order from the outside to the inside.
Example 1:
Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [1,2,3,6,9,8,7,4 ,5]
Example 2:
Input: matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
Output: [1,2,3,4,8 ,12,11,10,9,5,6,7]
限制：
0 <= matrix.length <= 100
0 <= matrix[i].length <= 100
Code
- Recursive thinking
- Get a clockwise number in the shape of "口" each time;
- For each "口" glyph, you only need to know the starting point coordinates (upper left point) and the number of rows and columns;
- Starting point coordinates, assuming (start_row, start_col)
- Number of rows, assuming row_len
- Number of columns, assuming col_len
- The “口” shape relationship between the outer layer and the inner layer is that the coordinates of the starting point are both +1, and the number of rows and columns are both -2.
- There are several different situations in the innermost layer:
- "." glyph, such as 3*3 matrix
- "一" font, such as 3*4 matrix
- "|" glyph, such as 4*3 matrix
- "口" glyph, such as 4*4 matrix
- Code
#include <algorithm>
#include <vector>
using namespace std;
class Solution {
public:
vector<int> spiralOrder(vector<vector<int>>& matrix) {
int row = matrix.size();
if (0 == row) {
return vector<int>();
}
int col = matrix[0].size();
if (0 == col) {
return vector<int>();
}
return getCircle(matrix, 0, 0, row, col);
}
private:
vector<int> getCircle(vector<vector<int>>& matrix,
int start_row,
int start_col,
int row_len,
int col_len) {
if (row_len < 1 || col_len < 1) {
return vector<int>();
}
vector<int> res;
if (1 == row_len && 1 == col_len) {
// .
res.push_back(matrix[start_row][start_col]);
} else if (1 == row_len) {
// ——
for (int i = 0; i < col_len; ++i) {
res.push_back(matrix[start_row][start_col + i]);
}
} else if (1 == col_len) {
// |
for (int i = 0; i < row_len; ++i) {
res.push_back(matrix[start_row + i][start_col]);
}
} else {
// 口
for (int i = 0; i < col_len; ++i) {
res.push_back(matrix[start_row][start_col + i]);
}
for (int i = 1; i < row_len; ++i) {
res.push_back(matrix[start_row + i][start_col + col_len - 1]);
}
for (int i = col_len - 2; i >= 0; --i) {
res.push_back(matrix[start_row + row_len - 1][start_col + i]);
}
for (int i = row_len - 2; i > 0; --i) {
res.push_back(matrix[start_row + i][start_col]);
}
}
auto inner_circle = getCircle(matrix, start_row + 1, start_col + 1,
row_len - 2, col_len - 2);
copy(inner_circle.begin(), inner_circle.end(), back_inserter(res));
return res;
}
};
test
#include <iostream>
int main() {
Solution s;
{
vector<vector<int>> matrix{
{
1, 2, 3, 4}, {
5, 6, 7, 8}, {
9, 10, 11, 12}};
auto res = s.spiralOrder(matrix);
for (auto i : res) {
cout << i << " ";
}
cout << endl;
}
{
vector<vector<int>> matrix{
{
3}, {
2}};
auto res = s.spiralOrder(matrix);
for (auto i : res) {
cout << i << " ";
}
}
cin.get();
return 0;
}
- result
1 2 3 4 8 12 11 10 9 5 6 7
3 2