Hard
Stamping the Grid — C++
Full explanation · Time O(m * n) · Space O(m * n)
// Time: O(m * n)
// Space: O(m * n)
class Solution {
public:
bool possibleToStamp(vector<vector<int>>& grid, int stampHeight, int stampWidth) {
vector<vector<int>> prefix(size(grid) + 1, vector<int>(size(grid[0]) + 1));
vector<vector<int>> fit(size(grid), vector<int>(size(grid[0])));
for (int i = 0; i < size(grid); ++i) {
for (int j = 0; j < size(grid[0]); ++j) {
prefix[i + 1][j + 1] = prefix[i + 1][j] + prefix[i][j + 1] - prefix[i][j] + (1 ^ grid[i][j]);
if (i + 1 >= stampHeight && j + 1 >= stampWidth) {
const int x = i + 1 - stampHeight, y = j + 1 - stampWidth;
fit[i][j] = static_cast<int>(prefix[i + 1][j + 1] - prefix[x][j + 1] - prefix[i + 1][y] + prefix[x][y] == stampWidth * stampHeight);
}
}
}
vector<vector<int>> prefix2(size(grid) + 1, vector<int>(size(grid[0]) + 1));
for (int i = 0; i < size(grid); ++i) {
for (int j = 0; j < size(grid[0]); ++j) {
prefix2[i + 1][j + 1] = prefix2[i + 1][j] + prefix2[i][j + 1] - prefix2[i][j] + fit[i][j];
}
}
for (int i = 0; i < size(grid); ++i) {
for (int j = 0; j < size(grid[0]); ++j) {
const int x = min(i + stampHeight, static_cast<int>(size(grid))), y = min(j + stampWidth, static_cast<int>(size(grid[0])));
if (!grid[i][j] && !(prefix2[x][y] - prefix2[i][y] - prefix2[x][j] + prefix2[i][j])) {
return false;
}
}
}
return true;
}
};