There is a square with m rows and n columns on the ground, and the horizontal and vertical coordinate ranges are 0∼m−1 and 0∼n−1 respectively.
。
A robot from coordinates (0,0)
The grid starts to move, and each time can only move one grid in four directions: left, right, up, and down.
But can not enter the sum of the digits of row and column coordinates is greater than k
grid.
How many squares can the robot reach?
Example 1
Input: k=7, m=4, n=5
Output: 20
Example 2
Input: k=18, m=40, n=40
Output: 1484
Explanation: When k is 18, the robot is able to enter square (35,37) because 3+5+3+7 = 18.
However, it cannot go into square (35,38) because 3+5+3+8 = 19.
Idea: Breadth-first search
class Solution {
private static class Node {
int first;
int second;
public Node(int first, int second) {
this.first = first;
this.second = second;
}
}
public int movingCount(int threshold, int rows, int cols) {
if (rows < 1 || cols < 1)
return 0;
boolean[][] visited = new boolean[rows][cols];
int[][] nxt = {
{
1, 0}, {
-1, 0}, {
0, 1}, {
0, -1}};
Queue<Node> que = new LinkedList<>();
visited[0][0] = true;
que.add(new Node(0, 0));
int res = 0;
while (!que.isEmpty()) {
Node popNode = que.poll();
res++;
for (int i = 0; i < nxt.length; i++) {
int fx = popNode.first + nxt[i][0], fy = popNode.second + nxt[i][1];
if (fx >= 0 && fy >= 0 && fx < rows && fy < cols && getSum(fx, fy) <= threshold && !visited[fx][fy]) {
que.add(new Node(fx, fy));
visited[fx][fy] = true;
}
}
}
return res;
}
private int getSum(int rows, int cols) {
int s = 0;
while (rows > 0) {
s += rows % 10;
rows /= 10;
}
while (cols > 0) {
s += cols % 10;
cols /= 10;
}
return s;
}
}