(Easy) Flipping an Image LeetCode

Posted 2020-11-10 CodingYM

Description:

Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image.

To flip an image horizontally means that each row of the image is reversed.  For example, flipping [1, 1, 0] horizontally results in [0, 1, 1].

To invert an image means that each 0 is replaced by 1, and each 1 is replaced by 0. For example, inverting [0, 1, 1] results in [1, 0, 0].

Example 1:

Input: [[1,1,0],[1,0,1],[0,0,0]]
Output: [[1,0,0],[0,1,0],[1,1,1]]
Explanation: First reverse each row: [[0,1,1],[1,0,1],[0,0,0]].
Then, invert the image: [[1,0,0],[0,1,0],[1,1,1]]

Example 2:

Input: [[1,1,0,0],[1,0,0,1],[0,1,1,1],[1,0,1,0]]
Output: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]
Explanation: First reverse each row: [[0,0,1,1],[1,0,0,1],[1,1,1,0],[0,1,0,1]].
Then invert the image: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]

Notes:

• 1 <= A.length = A[0].length <= 20
• 0 <= A[i][j] <= 1

 

 

Solution

class Solution {
    public int[][] flipAndInvertImage(int[][] A) {
        
        if(A==null || A.length ==0 ||A[0].length==0){
            return null;
        }
        
        int [][] Res = new int[A[0].length][];
        
        for(int i =0; i< A[0].length; i++){
            
            Res[i] = revert(A[i]);
        }
        
        return flip(Res);
    }
    
    
    public int[] revert (int[] A){
        
        int [] B = new int[A.length];
        
        for(int i=A.length-1;i>=0; i-- ){
            
            B[A.length-i-1] = A[i]; 
        }
        
        return B;
    }
    
    public int[][] flip(int[][] A){
        
        for (int i =0; i<A.length; i++){
            for(int j = 0; j<A[0].length; j++){
                if(A[i][j]==0){
                    A[i][j]=1;
                }
                else{
                    A[i][j]=0;
                }
            }
        }
        
        return A;
    }
}