Rectangle Sum Queries — Solution & Editorial
2-D prefix sums with inclusion–exclusion: sum = P[r2][c2] − P[r1−1][c2] − P[r2][c1−1] + P[r1−1][c1−1].
Complexity: O(NM + Q)
2-D prefix sums with inclusion–exclusion: sum = P[r2][c2] − P[r1−1][c2] − P[r2][c1−1] + P[r1−1][c1−1].
Complexity: O(NM + Q)