Jump Game && 45. Jump Game II

Jump Game

Given an array of non-negative integers, you is initially positioned at the first index of the array.

Each element of the array represents your maximum jump length is at that position.

Determine if you is able to reach the last index.

For example:
A = [2,3,1,1,4] , return true .

A = [3,2,1,0,4] , return false .

Greedy algorithm. Jump forward whenever possible, and if the last position is greater than the length, you can jump out.

public class Solution {
public boolean canjump (int[] nums) {
int maxindex = 0;
for (int i = 0; i < nums.length; i++) {
if (i > Maxindex) {
return false;
}
Maxindex = Math.max (Maxindex, i + nums[i]);
}
return true;
}
}

Jump Game II

Given an array of non-negative integers, you is initially positioned at the first index of the array.

Each element of the array represents your maximum jump length is at that position.

Your goal is to reach the last index in the minimum number of jumps.

For example:
Given array A =[2,3,1,1,4]

The minimum number of jumps to reach the last index is 2 . (Jump 1 Step from index 0 to 1 and then steps to the last 3 index.)

Still greedy, each walk to the maximum number of steps can be.

public class Solution {
public int jump (int[] nums) {
int jump = 0;
int i = 0;
int maxindex = 0;
while (Maxindex < nums.length-1) {
int curmax = Maxindex;
for (; I <= Curmax; i++) {
Maxindex = Math.max (Maxindex, nums[i] + i);
}
jump++;
if (Curmax = = Maxindex) return-1;
}
return jump;
}
}

Jump Game && 45. Jump Game II