45. Jump Game II | zhengxingxing

Method 1

You are given a 0-indexed array of integers nums of length n. You are initially positioned at nums[0].
Each element nums[i] represents the maximum length of a forward jump from index i. In other words, if you are at nums[i], you can jump to any nums[i + j] where:
- 0 <= j <= nums[i] and
- i + j < n
Return the minimum number of jumps to reach nums[n - 1]. The test cases are generated such that you can reach nums[n - 1].

Example 1

Input: nums = [2,3,1,1,4]
Output: 2
Explanation: The minimum number of jumps to reach the last index is 2. Jump 1 step from index 0 to 1, then 3 steps to the last index.

Example 2

Input: nums = [2,3,0,1,4]
Output: 2

Method 1

【O(n) time | O(1) space】

package Leetcode.Greedy;

/**
 * @author zhengxingxing
 * @date 2025/01/27
 */
public class JumpGameII {
    
    public static int jump(int[] nums) {
        // Counter for the minimum number of jumps needed
        int jumps = 0;
        // The farthest position that can be reached in the current jump
        int curEnd = 0;
        // The farthest position that can be reached considering all positions up to current position
        int curFarthest = 0;

        // Iterate through the array (except the last element as we don't need to jump from there)
        for (int i = 0; i < nums.length - 1; i++) {
            // Update the farthest position that can be reached from current position
            curFarthest = Math.max(curFarthest, i + nums[i]);

            // If we've reached the end of current jump range
            if (i == curEnd) {
                // We must take a jump
                jumps++;
                // Update the end range for the next jump
                curEnd = curFarthest;
            }
        }

        return jumps;
    }
    
    public static void main(String[] args) {
        // Test Case 1: Basic case with multiple possible paths
        int[] nums1 = {2,3,1,1,4};
        System.out.println("Test Case 1 Result: " + jump(nums1)); // Expected output: 2

        // Test Case 2: Another case with same minimum jumps but different path
        int[] nums2 = {2,3,0,1,4};
        System.out.println("Test Case 2 Result: " + jump(nums2)); // Expected output: 2

        // Test Case 3: Case where each step can only jump one position
        int[] nums3 = {1,1,1,1};
        System.out.println("Test Case 3 Result: " + jump(nums3)); // Expected output: 3
    }
}

Method 1

Enjoy Reading This Article?