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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]
.
class Solution {
public:
vector<int> spiralOrder(vector<vector<int>>& matrix) {
vector<vector<int> > dirs{{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
vector<int> res;
int nr = matrix.size(); if (nr == 0) return res;
int nc = matrix[0].size(); if (nc == 0) return res;
vector<int> nSteps{nc, nr-1};
int iDir = 0; // index of direction.
int ir = 0, ic = -1; // initial position
while (nSteps[iDir%2]) {
for (int i = 0; i < nSteps[iDir%2]; ++i) {
ir += dirs[iDir][0]; ic += dirs[iDir][1];
res.push_back(matrix[ir][ic]);
}
nSteps[iDir%2]--;
iDir = (iDir + 1) % 4;
}
return res;
}
};