/// https://leetcode.com/problems/spiral-matrix/
class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        vector<int> ans;
        int m = matrix.size();
        if(m==0) return ans;
        int n = matrix[0].size();
        if(n==0) return ans;
        
        int sr = 0, er = m-1, sc = 0, ec = n-1;
        int count = 0;
        
        while(sr<=er && sc<=ec){
            /// print sr
            for(int i=sc;i<=ec;i++){
                ans.push_back(matrix[sr][i]);
                count++;
            }
            sr++;
            if(count==m*n) return ans;
            
            /// print ec
            for(int i=sr;i<=er;i++){
                ans.push_back(matrix[i][ec]);
                count++;
            }
            ec--;
            if(count==m*n) return ans;
            
            /// print er
            for(int i=ec;i>=sc;i--){
                ans.push_back(matrix[er][i]);
                count++;
            }
            er--;
            if(count==m*n) return ans;
            
            /// print sc
            for(int i=er;i>=sr;i--){
                ans.push_back(matrix[i][sc]);
                count++;
            }
            sc++;
            if(count==m*n) return ans;
        }
        return ans;
    }
};