Minimum number of jumps DP VVIMP HARD

#User function Template for python3
class Solution:
    def minJumps(self, arr, n):
        if len(arr)==1:return 0
        if arr[0]==0:return -1

        maxreach,jmp,steps=arr[0],1,arr[0]
        for i in range(1,n):
            if i==n-1:return jmp
            maxreach=max(maxreach,i+arr[i])
            steps=steps-1
            if steps==0:
                jmp+=1
                '''
                Here we can understand if i>maxreach:return -1
                but why i>=maxreach? why not just i>maxreach?
                Here we have put i==maxreach also fails reaching
                destination because we computed already
                the maxreach by dng max(maxreach,i+arr[i) which didnt impact
                maxreach. So you can not move further
                '''
                if i>=maxreach:return -1
                else:steps=maxreach-i



#{
#  Driver Code Starts
#Initial Template for Python 3
if __name__ == '__main__':
    T=int(input())
    for i in range(T):
        n = int(input())
        Arr = [int(x) for x in input().split()]
        ob = Solution()
        ans = ob.minJumps(Arr,n)
        print(ans)
# } Driver Code Ends