#include <vector>//1011 O(n log S) O(1)
using namespace std;
static inline bool feasible(const int* a, int n, int days, int C){
    int need = 1, cur = 0;
    for(int i=0;i<n;++i){
        int x = a[i];
        if(cur + x > C){
            if(++need > days) return false;
            cur = x;// start next day with this package
        }else{
            cur += x;
        }
    }
    return true;
}
class Solution{
public:
    int shipWithinDays(vector<int>& w, int days){
        const int n = (int)w.size();
        const int* a = w.data();
        int L = 0, S = 0;// single pass: lower bound=max weight, upper bound=sum (both fit 32-bit)
        for(int i=0;i<n;++i){ int x=a[i]; if(x>L) L=x; S += x; }
        int R = S;
        if(days == n) return L;
        if(days == 1) return R;
        while(L < R){
            int m = (L + R) / 2;
            if(feasible(a, n, days, m)) R = m;  // feasible → try smaller
            else                      L = m + 1;// infeasible → increase
        }
        return L;// minimal feasible capacity
    }
};