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LeetCode(剑指 Offer)- 13. 机器人的运动范围


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解题思路

LeetCode(剑指 Offer)- 13. 机器人的运动范围_13. 机器人的运动范围

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AC 代码

  • Java
// 解决方案(1)
class Solution {

private int row, col, count, limit;

private boolean[][] path, no;

private int[] calc;

public int movingCount(int m, int n, int k) {
limit = k;
count = 0;
row = m;
col = n;
path = new boolean[m][n];
no = new boolean[m][n];
calc = new int[m * n];
dfs(0, 0);
return count;
}

private void dfs(int i, int j) {
if (i < 0 || i >= row || j < 0 || j >= col || path[i][j]) {
return;
}

path[i][j] = true;

if (cal(i) + cal(j) <= limit) {
count++;
} else {
no[i][j] = true;
// 此时站在限制位置, 必须马上回退, 这个最容易忘记
return;
}

// 接下来 4 个 if 为的是不进限制位置
if (i+1 < row && !no[i+1][j]) {
dfs(i + 1, j);
}

if (i-1 >= 0 && !no[i-1][j]) {
dfs(i - 1, j);
}

if (j+1 < col && !no[i][j+1]) {
dfs(i, j + 1);
}

if (j-1 >= 0 && !no[i][j-1]) {
dfs(i, j - 1);
}
}

private int cal(int num) {
int tnum = num;
if (calc[tnum] != 0) {
return calc[tnum];
}
int sum = 0;
while (num != 0) {
sum += num % 10;
num /= 10;
}
calc[tnum] = sum;
return sum;
}
}

// 解决方案(2)
class Solution {
int m, n, k;
boolean[][] visited;
public int movingCount(int m, int n, int k) {
this.m = m; this.n = n; this.k = k;
this.visited = new boolean[m][n];
return dfs(0, 0, 0, 0);
}
public int dfs(int i, int j, int si, int sj) {
if(i >= m || j >= n || k < si + sj || visited[i][j]) return 0;
visited[i][j] = true;
return 1 + dfs(i + 1, j, (i + 1) % 10 != 0 ? si + 1 : si - 8, sj) + dfs(i, j + 1, si, (j + 1) % 10 != 0 ? sj + 1 : sj - 8);
}
}

// 解决方案(3)
class Solution {
public int movingCount(int m, int n, int k) {
boolean[][] visited = new boolean[m][n];
int res = 0;
Queue<int[]> queue= new LinkedList<int[]>();
queue.add(new int[] { 0, 0, 0, 0 });
while(queue.size() > 0) {
int[] x = queue.poll();
int i = x[0], j = x[1], si = x[2], sj = x[3];
if(i >= m || j >= n || k < si + sj || visited[i][j]) continue;
visited[i][j] = true;
res ++;
queue.add(new int[] { i + 1, j, (i + 1) % 10 != 0 ? si + 1 : si - 8, sj });
queue.add(new int[] { i, j + 1, si, (j + 1) % 10 != 0 ? sj + 1 : sj - 8 });
}
return res;
}
}
  • C++
// 解决方案(1)
class Solution {
public:
int movingCount(int m, int n, int k) {
vector<vector<bool>> visited(m, vector<bool>(n, 0));
return dfs(0, 0, 0, 0, visited, m, n, k);
}
private:
int dfs(int i, int j, int si, int sj, vector<vector<bool>> &visited, int m, int n, int k) {
if(i >= m || j >= n || k < si + sj || visited[i][j]) return 0;
visited[i][j] = true;
return 1 + dfs(i + 1, j, (i + 1) % 10 != 0 ? si + 1 : si - 8, sj, visited, m, n, k) +
dfs(i, j + 1, si, (j + 1) % 10 != 0 ? sj + 1 : sj - 8, visited, m, n, k);
}
};

// 解决方案(2)
class Solution {
public:
int movingCount(int m, int n, int k) {
vector<vector<bool>> visited(m, vector<bool>(n, 0));
int res = 0;
queue<vector<int>> que;
que.push({ 0, 0, 0, 0 });
while(que.size() > 0) {
vector<int> x = que.front();
que.pop();
int i = x[0], j = x[1], si = x[2], sj = x[3];
if(i >= m || j >= n || k < si + sj || visited[i][j]) continue;
visited[i][j] = true;
res++;
que.push({ i + 1, j, (i + 1) % 10 != 0 ? si + 1 : si - 8, sj });
que.push({ i, j + 1, si, (j + 1) % 10 != 0 ? sj + 1 : sj - 8 });
}
return res;
}
};


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