Question

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 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

Solution 1

class Solution:
  def canReach(self, arr: List[int], start: int) -> bool:
    q = deque([start])
    while q:
      i = q.popleft()
      if arr[i] == 0:
        return True
      x = arr[i]
      arr[i] = -1
      for j in (i + x, i - x):
        if 0 <= j < len(arr) and arr[j] >= 0:
          q.append(j)
    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;
  }
}

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