g1301_1400.s1306_jump_game_iii.Solution Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of leetcode-in-java21 Show documentation

Java-based LeetCode algorithm problem solutions, regularly updated

There is a newer version: 1.38

package g1301_1400.s1306_jump_game_iii;

// #Medium #Array #Depth_First_Search #Breadth_First_Search
// #Graph_Theory_I_Day_11_Breadth_First_Search #Udemy_Arrays
// #2022_03_14_Time_2_ms_(96.23%)_Space_53.6_MB_(80.90%)

/**
 * 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 * 10⁴
 * *   `0 <= arr[i] < arr.length`
 * *   `0 <= start < arr.length`
**/
public class Solution {
    private boolean[] dp;
    private boolean found = false;

    public boolean canReach(int[] arr, int start) {
        if (arr[start] == 0) {
            return true;
        }
        dp = new boolean[arr.length];
        dp[start] = true;
        recurse(arr, start);
        return found;
    }

    private void recurse(int[] arr, int index) {
        if (found) {
            return;
        }
        if (index - arr[index] >= 0 && !dp[index - arr[index]]) {
            if (arr[index - arr[index]] == 0) {
                found = true;
                return;
            }
            dp[index - arr[index]] = true;
            recurse(arr, index - arr[index]);
        }
        if (index + arr[index] < arr.length && !dp[index + arr[index]]) {
            if (arr[index + arr[index]] == 0) {
                found = true;
                return;
            }
            dp[index + arr[index]] = true;
            recurse(arr, index + arr[index]);
        }
    }
}