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// 1905. Count Sub Islands
#include "leetcode.h"
/*
* you are given two 'm * n' binary matricies 'grid1', and 'grid2' containing
* only 0's (represeting water) and 1's (representing land). an island is a
* group of 1's connected 4 directionally (horizontal or vertical). any cells
* outside of the grid are considered water cells. an island in 'grid2' is
* considered a sub-island if there is an island in 'grid1' that contains all
* the cells that make up this island is 'grid2'. return the number of islands
* in 'grid2' that are considered sub islands
*/
int countSubIslands(int **grid1, int grid1Size, int *grid1ColSize, int **grid2,
int grid2Size, int *grid2ColSize) {
const int row = grid1Size, col = *grid1ColSize;
int cnt = 0, head, tail;
struct point {
int row, col;
} bfs_queue[col * row];
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
if (!grid2[i][j])
continue;
bool matched = true;
head = 0;
grid2[i][j] = 0;
bfs_queue[0].row = i;
bfs_queue[0].col = j;
tail = 1;
do {
const struct point curr = bfs_queue[head];
head++;
if (!grid1[curr.row][curr.col])
matched = false;
static const struct point offsets[] = {
{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
for (int k = 0; k < sizeof(offsets) / sizeof(offsets[0]); k++) {
const struct point next = {curr.row + offsets[k].row,
curr.col + offsets[k].col};
if ((next.row >= 0 && next.row < row) &&
(next.col >= 0 && next.col < col) && grid2[next.row][next.col]) {
grid2[next.row][next.col] = 0;
bfs_queue[tail] = next;
tail++;
}
}
} while (head < tail);
if (matched)
cnt++;
}
}
return cnt;
}
int main() {
int g11[5][5] = {{1, 1, 1, 0, 0},
{0, 1, 1, 1, 1},
{0, 0, 0, 0, 0},
{1, 0, 0, 0, 0},
{1, 1, 0, 1, 1}},
g11cs = 5;
int g21[5][5] = {{1, 1, 1, 0, 0},
{0, 0, 1, 1, 1},
{0, 1, 0, 0, 0},
{1, 0, 1, 1, 0},
{0, 1, 0, 1, 0}},
g21cs = 5;
int g12[5][5] = {{1, 0, 1, 0, 1},
{1, 1, 1, 1, 1},
{0, 0, 0, 0, 0},
{1, 1, 1, 1, 1},
{1, 0, 1, 0, 1}},
g12cs = 5;
int g22[5][5] = {{0, 0, 0, 0, 0},
{1, 1, 1, 1, 1},
{0, 1, 0, 1, 0},
{0, 1, 0, 1, 0},
{1, 0, 0, 0, 1}},
g22cs = 5;
printf("%d\n",
countSubIslands((int **)g11, ARRAY_SIZE(g11), &g11cs, (int **)g21,
ARRAY_SIZE(g21), &g21cs)); // expect: 3
printf("%d\n",
countSubIslands((int **)g12, ARRAY_SIZE(g12), &g12cs, (int **)g22,
ARRAY_SIZE(g22), &g22cs)); // expect: 2
}
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