[leetcode]Spiral Matrix

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int> > &matrix) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(matrix.empty()) return vector<int>();
        
        int M = matrix.size();
        int N = matrix[0].size();
        
        vector<int> result;
        
        int start = 0;
 
        int S = min(M, N);
        for(start = 0; start < S/2; start++){
            for(int j = start; j < N-start; j++){
                result.push_back(matrix[start][j]);
            }
            for(int i = start+1; i < M-start-1; i++){
                result.push_back(matrix[i][N-1-start]);
            }
            for(int j = N-1-start; j >= start; j--){
                result.push_back(matrix[M-1-start][j]);
            }
            for(int i = M-2-start; i>start; i--){
                result.push_back(matrix[i][start]);
            }
            
        }
        
        if(M <= N && M % 2 != 0){
            for(int j = start; j < N-start; j++){
                result.push_back(matrix[start][j]);
            }
        }
        
        if(N < M && N % 2 != 0){
            for(int i = start; i < M-start; i++){
                result.push_back(matrix[i][start]);
            }
        }
        
        
        return result;
        
        
    }
};