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Matrix traversal in spiral order (left to right)
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vector<int> spiralOrder(const vector<vector<int>> &A) { | |
vector<int> result; | |
int i = 0, j = 0; | |
int startI = 0, startJ = 1; | |
int rows = A.size(); | |
int cols = A[0].size(); | |
int total = rows*cols; | |
while (result.size() < total) { | |
// over a row | |
for (; i < cols; i++) { | |
if (result.size() == total) | |
return result; | |
result.push_back(A[j][i]); | |
} | |
// over a column | |
for (i--, j++; j < rows; j++) { | |
if (result.size() == total) | |
return result; | |
result.push_back(A[j][i]); | |
} | |
// go back in a row | |
for (j--, i--; i >= startI; i--) { | |
if (result.size() == total) | |
return result; | |
result.push_back(A[j][i]); | |
} | |
// go back in a column (avoid last item) | |
for (i++, j--; j >= startJ; j--) { | |
if (result.size() == total) | |
return result; | |
result.push_back(A[j][i]); | |
} | |
// restrict to inner rectangle and repeat | |
i++;j++; | |
startI++;startJ++; | |
cols--; rows--; | |
} | |
return result; | |
} |
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