0

Minimum number of jumps

Given an array of integers where each element represents the max number of steps that can be made forward from that element. Find the minimum number of jumps to reach the end of the array (starting from the first element). If an element is 0, then you cannot move through that element.

Example 1:

Input:

N=11 
arr=1 3 5 8 9 2 6 7 6 8 9

Output:

3

Explanation:

First jump from 1st element to 2nd element with value 3. Now, from here we jump to 5th element with value 9, and from here we will jump to last.

My Solution -

    // { Driver Code Starts
#include<bits/stdc++.h>
using namespace std;


 // } Driver Code Ends


// Function to return minimum number of jumps to end of array
int countJumps(int arr[], int i, int n, int dp[]){
  
    if(i>=n-1)
        return 0;
    if(dp[i]!=-2)
        return dp[i];
    if(arr[i]==0)
        return -1;
    if(arr[i]>=n)
        return 1;   
        
    int mn = INT_MAX, flag = 0;
    
    for(int j = 1; j<=arr[i]; j++){

        if(i+j>n-1)
            return 1;

        int temp = countJumps(arr,i+j,n,dp);

        if(temp==0){
            dp[i] = 1;
            return dp[i];
        }
        if(temp==-1){
            continue;
        }

        flag = 1;            
        mn = min(mn,temp);
    }
    
    if(flag == 0){
        return -1;
    }

    dp[i] = 1+mn;
    return dp[i];
}

int minJumps(int arr[], int n){
    // Your code here
    if(arr[0]==0)
        return -1;
    int dp[n];
    for(int i = 0; i<n; i++){
        dp[i] = -2;
    }
    return countJumps(arr,0,n,dp);
}


// { Driver Code Starts.

int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        int n,i,j;
        cin>>n;
        int arr[n];
        for(int i=0; i<n; i++)
            cin>>arr[i];
            
        cout<<minJumps(arr, n)<<endl;
    }
    return 0;
}
  // } Driver Code Ends
John Kugelman
  • 307,513
  • 65
  • 473
  • 519
harsh mehta
  • 11
  • 2
  • 7
    Thank you for providing the problem statement, the example input/output, and your code. All that is missing is an actual question. – paddy Feb 15 '21 at 07:41
  • Prefer `std::vector` here over `int arr[n];` VLA could be the problem here – Wander3r Feb 15 '21 at 07:43
  • The problem statement says that `n` can be up to 10 million. I don't think your stack is going to be large enough to allocate a VLA of 10 million `int` values. I would say that is definitely the problem, although there may be other problems too. – paddy Feb 15 '21 at 07:44
  • 3
    It's quite sad that sites such as this one teach you bad practices that are doomed to fail and then give you such tasks. You might want to read [Why should I not #include ?](https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h), [Why is “using namespace std;” considered bad practice?](https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice) and [Why aren't variable-length arrays part of the C++ standard?](https://stackoverflow.com/questions/1887097/why-arent-variable-length-arrays-part-of-the-c-standard) – churill Feb 15 '21 at 07:56

0 Answers0