Question Definition
Given a matrix consists of 0 and 1, find the distance of the nearest 0 for each cell.
The distance between two adjacent cells is 1. Example 1: Input:
0 0 0
0 1 0
0 0 0
Output:
0 0 0
0 1 0
0 0 0
Example 2: Input:
0 0 0
0 1 0
1 1 1
Output:
0 0 0
0 1 0
1 2 1
Note:
- The number of elements of the given matrix will not exceed 10,000.
- There are at least one 0 in the given matrix.
- The cells are adjacent in only four directions: up, down, left and right.
Java Solution
public int[][] updateMatrix(int[][] matrix) {
int m = matrix.length;
int n = matrix[0].length;
Queue<int[]> queue = new LinkedList<>();
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (matrix[i][j] == 0) {
queue.offer(new int[] {i, j});
}
else {
matrix[i][j] = Integer.MAX_VALUE;
}
}
}
int[][] dirs = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
while (!queue.isEmpty()) {
int[] cell = queue.poll();
for (int[] d : dirs) {
int r = cell[0] + d[0];
int c = cell[1] + d[1];
if (r < 0 || r >= m || c < 0 || c >= n ||
matrix[r][c] <= matrix[cell[0]][cell[1]] + 1) continue;
queue.add(new int[] {r, c});
matrix[r][c] = matrix[cell[0]][cell[1]] + 1;
}
}
return matrix;
}
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