g0901_1000.s0980_unique_paths_iii.Solution Maven / Gradle / Ivy
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Java-based LeetCode algorithm problem solutions, regularly updated
package g0901_1000.s0980_unique_paths_iii;
// #Hard #Array #Matrix #Bit_Manipulation #Backtracking
// #2022_03_31_Time_0_ms_(100.00%)_Space_39.3_MB_(98.32%)
public class Solution {
private final int[] row = {0, 0, 1, -1};
private final int[] col = {1, -1, 0, 0};
private int isSafe(int[][] grid, int rows, int cols, int i, int j) {
if (i < 0 || j < 0 || i >= rows || j >= cols || grid[i][j] == -1) {
return 0;
}
if (grid[i][j] == 2) {
for (int l = 0; l < rows; l++) {
for (int m = 0; m < cols; m++) {
if (grid[l][m] == 0) {
/* Return 0 if all zeros in the path are not covered */
return 0;
}
}
}
/* Return 1, as we covered all zeros in the path */
return 1;
}
/* mark as visited */
grid[i][j] = -1;
int result = 0;
for (int k = 0; k < 4; k++) {
/* travel in all four directions (up,down,right,left) */
result = result + isSafe(grid, rows, cols, (i + row[k]), (j + col[k]));
}
/* Mark unvisited again to backtrack */
grid[i][j] = 0;
return result;
}
public int uniquePathsIII(int[][] grid) {
int rows = grid.length;
int cols = grid[0].length;
int result = 0;
for (int k = 0; k < rows; k++) {
for (int m = 0; m < cols; m++) {
if (grid[k][m] == 1) {
/* find indexes where 1 is located and start covering paths */
result = isSafe(grid, rows, cols, k, m);
break;
}
}
}
return result;
}
}