1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
// 304. Range Sum Query 2D - Immutable
#include "leetcode.h"
/*
* given a 2d matrix 'matrix', handle multiple queries of the following type:
* calculate the sum of the elements of 'matrix' inside the rectangle defined by
* its upper left corner '(row1, col1)' and lower right corer '(row2, col2)'.
* you must design an algorithm where 'sumRegion' works on 'O(1)' time
* complexity.
*/
typedef struct {
int **matrix;
int matrixSize;
} NumMatrix;
NumMatrix *numMatrixCreate(int **matrix, int matrixSize, int *matrixColSize) {
NumMatrix *obj = (NumMatrix *)malloc(matrixSize * sizeof(NumMatrix));
obj->matrix = (int **)malloc((matrixSize + 1) * sizeof(NumMatrix));
obj->matrixSize = matrixSize + 1;
for (int i = 0; i <= matrixSize; i++)
obj->matrix[i] = (int *)calloc(*matrixColSize + 1, sizeof(int));
for (int i = 1; i <= matrixSize; i++)
for (int j = 1; j <= *matrixColSize; j++)
obj->matrix[i][j] = (obj->matrix[i - 1][j] + obj->matrix[i][j - 1] -
obj->matrix[i - 1][j - 1] + matrix[i - 1][j - 1]);
return obj;
}
int numMatrixSumRegion(NumMatrix *obj, int row1, int col1, int row2, int col2) {
return (obj->matrix[row2 + 1][col2 + 1] - obj->matrix[row2 + 1][col1] -
obj->matrix[row1][col2 + 1] + obj->matrix[row1][col1]);
}
void numMatrixFree(NumMatrix *obj) {
for (int i = 0; i < obj->matrixSize; i++)
free(obj->matrix[i]);
free(obj->matrix);
free(obj);
}
int main() {
int matrix_input[5][5] = {{3, 0, 1, 4, 2},
{5, 6, 3, 2, 1},
{1, 2, 0, 1, 5},
{4, 1, 0, 1, 7},
{1, 0, 3, 0, 5}};
struct two_d_arr matrix;
two_d_arr_init(&matrix, 5, 5, matrix_input);
NumMatrix *obj =
numMatrixCreate(matrix.arr, matrix.row_size, matrix.col_size);
printf("%d\n", numMatrixSumRegion(obj, 2, 1, 4, 3)); // expect: 8
printf("%d\n", numMatrixSumRegion(obj, 1, 1, 2, 2)); // expect: 11
printf("%d\n", numMatrixSumRegion(obj, 1, 2, 2, 4)); // expect: 12
numMatrixFree(obj);
two_d_arr_free(&matrix);
}
|