Formatted question description: https://leetcode.ca/all/1306.html
1306. Jump Game III (Medium)
Given an array of non-negative integers arr, you are initially positioned at start index of the array. When you are at index i, you can jump to i + arr[i] or i - arr[i], check if you can reach to any index with value 0.
Notice that you can not jump outside of the array at any time.
Example 1:
Input: arr = [4,2,3,0,3,1,2], start = 5 Output: true Explanation: All possible ways to reach at index 3 with value 0 are: index 5 -> index 4 -> index 1 -> index 3 index 5 -> index 6 -> index 4 -> index 1 -> index 3
Example 2:
Input: arr = [4,2,3,0,3,1,2], start = 0 Output: true Explanation: One possible way to reach at index 3 with value 0 is: index 0 -> index 4 -> index 1 -> index 3
Example 3:
Input: arr = [3,0,2,1,2], start = 2 Output: false Explanation: There is no way to reach at index 1 with value 0.
Constraints:
1 <= arr.length <= 5 * 10^40 <= arr[i] < arr.length0 <= start < arr.length
Related Topics:
Breadth-first Search, Graph
Similar Questions:
Solution 1. DFS
// OJ: https://leetcode.com/problems/jump-game-iii/
// Time: O(N)
// Space: O(N)
class Solution {
public:
bool canReach(vector<int>& A, int start) {
if (start < 0 || start >= A.size() || A[start] < 0) return false;
if (A[start] == 0) return true;
A[start] *= -1;
return canReach(A, start + A[start]) || canReach(A, start - A[start]);
}
};
Solution 2. BFS
// OJ: https://leetcode.com/problems/jump-game-iii/
// Time: O(N)
// Space: O(N)
class Solution {
public:
bool canReach(vector<int>& A, int start) {
queue<int> q;
q.push(start);
while (q.size()) {
int i = q.front();
q.pop();
if (A[i] == 0) return true;
if (A[i] < 0) continue;
if (i + A[i] < A.size()) q.push(i + A[i]);
if (i - A[i] >= 0) q.push(i - A[i]);
A[i] *= -1;
}
return false;
}
};
Java
class Solution {
public boolean canReach(int[] arr, int start) {
int length = arr.length;
boolean[] canReach = new boolean[length];
canReach[start] = true;
Queue<Integer> queue = new LinkedList<Integer>();
queue.offer(start);
while (!queue.isEmpty()) {
int index = queue.poll();
int step = arr[index];
int left = index - step, right = index + step;
if (left >= 0) {
if (arr[left] == 0)
return true;
else if (!canReach[left]) {
canReach[left] = true;
queue.offer(left);
}
}
if (right < length) {
if (arr[right] == 0)
return true;
else if (!canReach[right]) {
canReach[right] = true;
queue.offer(right);
}
}
}
return false;
}
}