README_EN.md

1306. Jump Game III

中文文档

Description

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 * 104
• 0 <= arr[i] < arr.length
• 0 <= start < arr.length

Solutions

BFS.

Python3

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

Java

class Solution {
    public boolean canReach(int[] arr, int start) {
        int n = arr.length;
        Deque<Integer> q = new ArrayDeque<>();
        q.offer(start);
        while (!q.isEmpty()) {
            int i = q.poll();
            if (arr[i] == 0) {
                return true;
            }
            for (int j : Arrays.asList(i + arr[i], i - arr[i])) {
                if (j >= 0 && j < n && arr[j] >= 0) {
                    q.offer(j);
                }
            }
            arr[i] = -1;
        }
        return false;
    }
}

C++

class Solution {
public:
    bool canReach(vector<int>& arr, int start) {
        int n = arr.size();
        queue<int> q {{start}};
        while (!q.empty()) {
            int i = q.front();
            if (arr[i] == 0)
                return 1;
            q.pop();
            for (int j : {i + arr[i], i - arr[i]}) {
                if (j >= 0 && j < n && arr[j] >= 0)
                    q.push(j);
            }
            arr[i] = -1;
        }
        return 0;
    }
};

Go

func canReach(arr []int, start int) bool {
	q := []int{start}
	for len(q) > 0 {
		i := q[0]
		if arr[i] == 0 {
			return true
		}
		q = q[1:]
		for _, j := range []int{i + arr[i], i - arr[i]} {
			if j >= 0 && j < len(arr) && arr[j] >= 0 {
				q = append(q, j)
			}
		}
		arr[i] = -1
	}
	return false
}

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