GFG PTOD | 18 Dec | Allocate Minimum Pages

bool isPossible(int k, int mid, const vector<int> &arr) {
        int students = 1, curPage = 0;
        
        for(pages : arr) {
            if(pages > mid) return false;
            
            if(curPage + pages > mid) {
                students++;
                curPage = pages;
                if(students > k) return false;
            } else {
                curPage += pages;
            }
        }
        return true;
    }
  
    int findPages(vector<int> &arr, int k) {
        // code here
        if(k > arr.size()) return -1;
        int ret = -1;
        int low = *max_element(arr.begin(), arr.end()); // max value in array
        int high = accumulate(arr.begin(), arr.end(), 0); // sum of all elements in array
        
        while(low <= high) {
            int mid = low + (high-low) /2;
            
            if(isPossible(k, mid, arr)) {
                ret = mid;
                high = mid-1;
            } else {
                low = mid+1;
            }
        }
        
        return ret;
    }