<p>A conveyor belt has packages that must be shipped from one port to another within <code>days</code> days.</p>

<p>The <code>i<sup>th</sup></code> package on the conveyor belt has a weight of <code>weights[i]</code>. Each day, we load the ship with packages on the conveyor belt (in the order given by <code>weights</code>). We may not load more weight than the maximum weight capacity of the ship.</p>

<p>Return the least weight capacity of the ship that will result in all the packages on the conveyor belt being shipped within <code>days</code> days.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> weights = [1,2,3,4,5,6,7,8,9,10], days = 5
<strong>Output:</strong> 15
<strong>Explanation:</strong> A ship capacity of 15 is the minimum to ship all the packages in 5 days like this:
1st day: 1, 2, 3, 4, 5
2nd day: 6, 7
3rd day: 8
4th day: 9
5th day: 10

Note that the cargo must be shipped in the order given, so using a ship of capacity 14 and splitting the packages into parts like (2, 3, 4, 5), (1, 6, 7), (8), (9), (10) is not allowed.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> weights = [3,2,2,4,1,4], days = 3
<strong>Output:</strong> 6
<strong>Explanation:</strong> A ship capacity of 6 is the minimum to ship all the packages in 3 days like this:
1st day: 3, 2
2nd day: 2, 4
3rd day: 1, 4
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> weights = [1,2,3,1,1], days = 4
<strong>Output:</strong> 3
<strong>Explanation:</strong>
1st day: 1
2nd day: 2
3rd day: 3
4th day: 1, 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= days &lt;= weights.length &lt;= 5 * 10<sup>4</sup></code></li>
	<li><code>1 &lt;= weights[i] &lt;= 500</code></li>
</ul>


class Solution {
public:
    int findmax(vector<int> arr) {
        int n = arr.size() ; 
        int maxi = INT_MIN ;

        for(int i=0 ;i<n ;i++)
        {
            maxi= std::max(maxi , arr[i]) ; 
        }
        return maxi ; 
    }

    int sum(vector<int> arr) {
        int sum =0 ; 
        int n=arr.size() ;
        for(int i=0 ;i<n ;i++){
            sum += arr[i] ; 
        } 
        return sum ; 
    }

    int calculateStudent(vector<int>arr , int pages) {
        int sum = 0 ; 
        int student = 1 ;
        int n = arr.size(); 

        for(int i=0 ;i<n ;i++) {

            if(sum + arr[i] <= pages) {
                sum +=arr[i] ; 
            }
            else{
                student++; 
                sum = arr[i] ; 
            }
        }
        return student; 
    }

    int linearsol(vector<int>& arr, int k ,int low , int high) {

        for(int i=low; i<=high ; i++) {
            int temp = calculateStudent(arr , i) ; 
            if(temp == k) {
                return i ; 
            }
        }
        return low ; 
    }
    int binarysol(vector<int>& arr, int k ,int low , int high) {

        int tlow = low ; 
        int thigh = high; 
        int mid = (thigh + tlow )/2 ; 
        int ans = -1 ;

        while(tlow <= thigh) {
            int temp = calculateStudent(arr , mid) ;

            if(temp > k){
                tlow = mid+1 ;
            }else{
                ans = mid ; 
                thigh = mid-1;
            }
           mid = (thigh + tlow )/2 ; 
        }
        return ans; 
    }

    int splitArray(vector<int>& nums, int k) {
        
        int low = findmax(nums); 
        int high = sum(nums) ; 

        if(k==1){
            return high ; 
        }

        // int ans = linearsol(nums,k ,low ,high) ; 
        int ans = binarysol(nums,k,low ,high) ; 

        return ans ; 

        // for(int i=low ;i<high ;i++ ) {
            
        // }
    } 
    int shipWithinDays(vector<int>& weights, int days) {
       int ans = splitArray(weights ,days) ;
        return ans ; 
    }
};
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