Welcome to Subscribe On Youtube

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 * 10^4
  • 0 <= arr[i] < arr.length
  • 0 <= 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;
    }
};
  • 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;
        }
    }
    
    ############
    
    class Solution {
        public boolean canReach(int[] arr, int start) {
            Deque<Integer> q = new ArrayDeque<>();
            q.offer(start);
            while (!q.isEmpty()) {
                int i = q.poll();
                if (arr[i] == 0) {
                    return true;
                }
                int x = arr[i];
                arr[i] = -1;
                for (int j : List.of(i + x, i - x)) {
                    if (j >= 0 && j < arr.length && arr[j] >= 0) {
                        q.offer(j);
                    }
                }
            }
            return false;
        }
    }
    
  • // 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]);
        }
    };
    
  • class Solution:
        def canReach(self, arr: List[int], start: int) -> bool:
            n = len(arr)
            q = deque([start])
            while q:
                i = q.popleft()
                if arr[i] == 0:
                    return True
                for j in [i + arr[i], i - arr[i]]:
                    if 0 <= j < n and arr[j] >= 0:
                        q.append(j)
                arr[i] = -1
            return False
    
    
    
  • func canReach(arr []int, start int) bool {
    	q := []int{start}
    	for len(q) > 0 {
    		i := q[0]
    		q = q[1:]
    		if arr[i] == 0 {
    			return true
    		}
    		x := arr[i]
    		arr[i] = -1
    		for _, j := range []int{i + x, i - x} {
    			if j >= 0 && j < len(arr) && arr[j] >= 0 {
    				q = append(q, j)
    			}
    		}
    	}
    	return false
    }
    
  • function canReach(arr: number[], start: number): boolean {
        const q: number[] = [start];
        while (q.length) {
            const i: number = q.shift()!;
            if (arr[i] === 0) {
                return true;
            }
            const x: number = arr[i];
            arr[i] = -1;
            for (const j of [i + x, i - x]) {
                if (j >= 0 && j < arr.length && arr[j] !== -1) {
                    q.push(j);
                }
            }
        }
        return false;
    }
    
    

All Problems

All Solutions