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EscapeSpreadingFire.java
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EscapeSpreadingFire.java
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class Solution {
int m, n;
int[][] grid, copy;
boolean[][] visited;
boolean fireSpread;
private boolean helper(int wt) {
for(int i=0; i<wt; i++) {
if(!spread()) {
break;
}
}
return dfs(0, 0);
}
private boolean call(int i, int j) {
if(isValidFree(i, j) && !visited[i][j]) {
return dfs(i, j);
}
return false;
}
private boolean dfs(int i, int j) {
if(i == m-1 && j == n-1) {
return true;
}
if(visited[i][j]) {
return false;
}
fireSpread = spread();
visited[i][j] = true;
boolean found = false;
found = call(i+1, j);
if(!found) found = call(i-1, j);
if(!found) found = call(i, j-1);
if(!found) found = call(i, j+1);
return found;
}
private boolean isValid(int i, int j) {
return i >= 0 && i < m && j >= 0 && j < n;
}
private boolean isFree(int i, int j) {
return copy[i][j] == 0;
}
private boolean isValidFree(int i, int j) {
return isValid(i, j) && isFree(i, j);
}
private boolean spread() {
int cnt = 0;
for(int i=0; i<m; i++) {
for(int j=0; j<n; j++) {
if(copy[i][j] == 1) {
if(isValidFree(i-1, j)) {
copy[i-1][j] == 3;
cnt++;
}
if(isValidFree(i+1, j)) {
copy[i+1][j] == 3;
cnt++;
}
if(isValidFree(i, j-1)) {
copy[i][j-1] == 3;
cnt++;
}
if(isValidFree(i, j+1)) {
copy[i][j+1] == 3;
cnt++;
}
}
}
}
if(cnt != 0) {
for(int i=0; i<m; i++) {
for(int j=0; j<n; j++) {
if(copy[i][j] == 3) {
copy[i][j] == 1;
}
}
}
}
return cnt != 0;
}
private void initCopy() {
for(int i=0; i<m; i++) {
for(int j=0; j<n; j++) {
copy[i][j] = grid[i][j];
}
}
}
private void initVis() {
for(int i=0; i<m; i++) {
for(int j=0; j<n; j++) {
visited[i][j] = false;
}
}
}
public int maximumMinutes(int[][] g) {
grid = g;
m = grid.length;
n = grid[0].length;
copy = new int[m][n];
visited = new boolean[m][n];
int res = 0;
fireSpread = true;
while(true) {
initCopy();
initVis();
boolean found = helper(res);
if(found && !fireSpread) {
return 1000_000_000;
} else if(!found && res == 0) {
return -1;
} else if(!found) {
break;
}
res++;
}
return res;
}
}