Create Function for Convert 2d array into 1D array
But at Declaration time the size of 1D array how to give size to the new 1D array
int[] convert(int[][] input){
int[] result;
int z=0;
for(int row=0;row<input.length;row++) {
for(int col=0;col<input[row].length;col++) {
result[z]=input[row][col];
z++;
}
}
return result;/* Error comes here For Initialization. How to initialize before Knowing size*/
}
if rows and columns are balanced
int result[] = new int[input.length * input[0].length];
otherwise, you have to loop through the whole array while keeping a count of length
int len = 0;
for(int[] a : input){
len+=a.length;
}
int[] result = new int[len];
You can simply compute the size this way (i.e number of rows * number of columns):
int[] result = new int[input.length * input[0].length] ;
1)If it is rectangular 2D array, compute the size this way
int array[] = new int[input.length * input[0].length];
2)If it is not rectangular, iterate through each row and add the length of each sub-array
int size = 0;
for(int i=0;i<input.length;i++){
size += input[i].length;
}
Or you could just use streams with out to have to take care of size by yourself:
int[] convert(int[][] input){
return Stream.of(input).flatMapToInt(x -> Arrays.stream(x)).toArray();
}
The below code converts / flattens 2D array to 1D (row-wise)
(MxM)- Row Wise
private static int[] convert2Dto1DArrayMxM(int[][] input) {
//Get total elements to calculate the length of result Array
//Since it is MXM totalElements calculation is = rowsLength x row[0].length
int totalElements = input.length * input[0].length;
//Populate the result Array
int[] result = new int[totalElements];
int resultIndex = 0;
for (int row = 0; row < input.length; row++) {
for (int col = 0; col < input[0].length; col++) {
result[resultIndex] = input[row][col];
resultIndex++;
}
}
return result;
}
(MxN)- Row Wise
private static int[] convert2Dto1DArrayMxN(int[][] input) {
//Get total elements in input array to calculate the length of result Array
int totalElements = 0;
for (int row = 0; row < input.length; row++) {
for (int col = 0; col < input[row].length; col++) {
totalElements++;
}
}
//Populate the result Array
int[] result = new int[totalElements];
int resultIndex = 0;
for (int row = 0; row < input.length; row++) {
for (int col = 0; col < input[row].length; col++) {
result[resultIndex] = input[row][col];
resultIndex++;
}
}
return result;
}
(MxM)- Column Wise
private static int[] convert2Dto1DArrayMxMColumnWise(int[][] input) {
//Get total elements to calculate the length of result Array
//Since it is MXM totalElements calculation is = rowsLength x row[0].length
int totalElements = input.length * input[0].length;
//Populate the result Array
int[] result = new int[totalElements];
int resultIndex = 0;
for (int column = 0; column < input[0].length; column++) {
for (int row = 0; row < input.length; row++) {
result[resultIndex] = input[row][column];
resultIndex++;
}
}
return result;
}
How to use:
public static void main(String[] args) {
//MXM - Row Wise
int[][] mXm = {{2, 19}, {6, 80}, {42, 10}};
int[] mXmResult = convert2Dto1DArrayMxM(mXm);
System.out.println(Arrays.toString(mXmResult));
//MXN - Row Wise
int[][] mXn = {{2, 19, 0, 1, 4, 6, 3, 2, 1, 6}, {2, 0}, {2, 0, 1, 5}};
int[] mXnResult = convert2Dto1DArrayMxN(mXn);
System.out.println(Arrays.toString(mXnResult));
//MxM - Column Wise
int[][] mXmColumnWise = {{2, 19,10}, {6, 80,9}};
int[] mXmResultColumnWise = convert2Dto1DArrayMxMColumnWise(mXmColumnWise);
System.out.println(Arrays.toString(mXmResultColumnWise));
}
Sample output for the above main()
MxM - Row Wise [2, 19, 6, 80, 42, 10]
MxN - Row Wise [2, 19, 0, 1, 4, 6, 3, 2, 1, 6, 2, 0, 2, 0, 1, 5]
MxM - Column Wise [2, 6, 19, 80, 10, 9]
