// Perform the precomputation step here
GridSum::GridSum (TwoD_Array<int>& grid) {
// TODO
int left;
int top;
int topLeft;
//TwoD_Array<int> grid(size, size);
pg = new TwoD_Array<int>(grid.getNumRows(),grid.getNumCols());
pg->at(0,0) = grid.at(0,0); //initialize (0,0) to the grid(0,0)
for(int i = 0; i < grid.getNumRows(); i++){
for(int j = 0; j < grid.getNumCols(); j++){
if(i == 0 && j ==0){ //special case, already handled
continue;
}
else if(j == 0){
left = 0; //LEFT IS EMPTY
top = pg->at(i-1,j);
topLeft = 0;
}
else if(i == 0){
top = 0; //TOP IS EMPTY
left = pg->at(i,j-1);
topLeft = 0;
}
else{
left = pg->at(i,j-1);
top = pg->at(i-1,j);
topLeft = pg->at(i-1,j-1);
}
pg->at(i,j) = grid.at(i,j) + left + top - topLeft;
}
}
}
// Perform the precomputation step here
GridSum::GridSum (TwoD_Array<int>& grid) {
// TODO
//calculate N size for the matrix
int N = grid.getNumRows();
//Initilize the 2D array for pre-computation
pg = new TwoD_Array<int> (N,N);
int row = grid.getNumRows();
int col = grid.getNumCols();
pg->at(0,0) = grid.at(0,0);
for(int i = 0; i < row; i++){
for(int j = 0; j < col; j ++){
if(i == 0 && j == 0) continue;
//handle the first row
if(!hasAboveElement(i)){
//if no above, just add left
pg->at(i,j) = grid.at(i,j) + pg->at(i,j-1);
}
if(!hasLeftElement(j)) {
//if no left just add above
pg->at(i,j) = grid.at(i,j) + pg->at(i-1,j);
}
//set the current cordiation as the sum of current and the one above
if(hasAboveElement(i) && hasLeftElement(j)) {
pg->at(i,j) = pg->at(i-1,j) + pg->at(i,j-1) - pg->at(i-1,j-1) + grid.at(i,j);
}
}
}
//pg->printOut();
}
// Perform the precomputation step here
// Compute sum for (0, 0) to (n, m)
GridSum::GridSum (TwoD_Array<int>& grid) {
// TODO
int colSum = 0;
pg = new TwoD_Array<int>(grid.getNumRows(), grid.getNumCols());
pg->at(0, 0) = grid.at(0, 0);
//first row of sum aray
for(int col = 1; col < grid.getNumCols(); col++) {
pg->at(0, col) = pg->at(0, col - 1) + grid.at(0, col);
}
//first colomn of sum array
for(int row = 1; row < grid.getNumRows(); row++) {
pg->at(row, 0) = pg->at(row - 1, 0) + grid.at(row, 0);
}
for(int col = 1; col < grid.getNumCols(); col++) {
colSum = grid.at(0, col);
for(int row = 1; row < grid.getNumRows(); row++) {
pg->at(row, col) = pg->at(row, col - 1) + grid.at(row, col) + colSum;
colSum += grid.at(row, col);
}
}
}