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1306. Jump Game III

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

BFS.

• Java
• C++
• Python
• Go
• TypeScript

• 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;
      }
  };
  

• 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
  
  

• 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;
  }
  
  

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