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// 778. Swim in Rising Water
#include "leetcode.h"
/*
* you are given an 'n x n' integer matrix 'grid' where each value 'grid[i][j]'
* represnts the elevation at that point '(i, j)'. it starts raining and water
* gradually rises over time. at time 't', the water level is 't', meaning any
* cell with elevation less than or equal to 't' is submerged or reachable. you
* can swim from a square to another 4-direction adjacent square if and only if
* the elevation of both squares individually are at most 't'. you can swim
* infinite distances in zero time. of course, you must stay within the
* boundaries of the grid. return the minimum time until you can reach the
* bottom right . you can swim infinite distances in zero time. of course, you
* must stay within the boundaries of the grid. return the minimum time until
* you can reach the bottom right square if you start at the top left. you can
* swim infinite distances in zero time. of course, you must stay within the
* boundaries of the grid. return the minimum time until you can reach the
* bottom right square if you start at the top left..square if you start at the
* top left.
*/
static int dir[4][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
struct node {
int val;
int row;
int col;
};
struct pq {
int size;
int capacity;
struct node *data;
};
void swap(struct node *a, struct node *b) {
struct node tmp = *a;
*a = *b;
*b = tmp;
}
struct pq *pq_init(int capacity) {
struct pq *obj = (struct pq *)malloc(sizeof(struct pq));
obj->size = 0;
obj->capacity = capacity;
obj->data = (struct node *)malloc(capacity * sizeof(struct node));
return obj;
}
void pq_free(struct pq *obj) {
free(obj->data);
free(obj);
}
void min_heapify(struct pq *obj, int idx) {
int smallest = idx, left = idx * 2 + 1, right = idx * 2 + 2;
if (left < obj->size && obj->data[left].val < obj->data[smallest].val)
smallest = left;
if (right < obj->size && obj->data[right].val < obj->data[smallest].val)
smallest = right;
if (smallest != idx) {
swap(&obj->data[idx], &obj->data[smallest]);
min_heapify(obj, smallest);
}
}
void push(struct pq *obj, int val, int row, int col) {
int idx = obj->size;
struct node n = {val, row, col};
obj->data[(obj->size)++] = n;
while (idx && obj->data[(idx - 1) / 2].val > obj->data[idx].val) {
swap(&obj->data[(idx - 1) / 2], &obj->data[idx]);
idx = (idx - 1) / 2;
}
}
struct node pop(struct pq *obj) {
struct node root = obj->data[0];
obj->data[0] = obj->data[--(obj->size)];
min_heapify(obj, 0);
return root;
}
bool is_empty(struct pq *obj) { return !obj->size; }
int swimInWater(int **grid, int gridSize, int *gridColSize) {
int total = gridSize * (*gridColSize);
struct pq *heap = pq_init(total);
push(heap, grid[0][0], 0, 0);
grid[0][0] = -1;
while (!is_empty(heap)) {
struct node tmp = pop(heap);
for (int i = 0; i < 4; i++) {
int x = tmp.row + dir[i][0];
int y = tmp.col + dir[i][1];
if (x >= 0 && x < gridSize && y >= 0 && y < *gridColSize &&
grid[x][y] != -1) {
int max = grid[x][y] > tmp.val ? grid[x][y] : tmp.val;
if (x == gridSize - 1 && y == (*gridColSize) - 1) {
pq_free(heap);
return max;
}
push(heap, max, x, y);
grid[x][y] = -1;
}
}
}
pq_free(heap);
return 0;
}
int main() {
int g1i[2][2] = {{0, 2}, {1, 3}}, g2i[5][5] = {{0, 1, 2, 3, 4},
{24, 23, 22, 21, 5},
{12, 13, 14, 15, 16},
{11, 17, 18, 19, 20},
{10, 9, 8, 7, 6}};
struct two_d_arr *g1 =
two_d_arr_init(ARRAY_SIZE(g1i), ARRAY_SIZE(g1i[0]), g1i);
struct two_d_arr *g2 =
two_d_arr_init(ARRAY_SIZE(g2i), ARRAY_SIZE(g2i[0]), g2i);
printf("%d\n", swimInWater(g1->arr, g1->row_size, g1->col_size)); // expect: 3
printf("%d\n", swimInWater(g2->arr, g2->row_size, g2->col_size)); // expect:
// 16
two_d_arr_free(g1);
two_d_arr_free(g2);
}
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