Spiral Matrix II

Desicription

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:

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[
[ 1, 2, 3 ],
[ 8, 9, 4 ],
[ 7, 6, 5 ]
]

Solution

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class Solution {
private:
bool isValid(vector<vector<int> >& matrix, int x, int y, int n){
if(x < 0 || x >= n || y < 0 || y >= n || matrix[x][y] == INT_MIN)
return 0;
return 1;
}
public:
vector<vector<int>> generateMatrix(int n) {
vector<vector<int>> matrix(n, vector<int>(n, 0));
vector<vector<int>> res(n, vector<int>(n, 0));
int x = 0;
int y = 0;
int val = 1;
while(1){
bool flag = 0;
while(isValid(matrix, x, y, n))
res[x][y] = val++, matrix[x][y] = INT_MIN, y++, flag = 1;
y--;
x++;
while(isValid(matrix, x, y, n))
res[x][y] = val++, matrix[x][y] = INT_MIN, x++, flag = 1;
x--;
y--;
while(isValid(matrix, x, y, n))
res[x][y] = val++, matrix[x][y] = INT_MIN, y--, flag = 1;
y++;
x--;
while(isValid(matrix, x, y, n))
res[x][y] = val++, matrix[x][y] = INT_MIN, x--, flag = 1;
x++;
y++;
if(!flag)
return res;
}
}
};