Code Only Works for A Few Cases

Problems and Contests
#1

I’m doing Sleeping In Class, but my code only works for some of the cases.

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

class Main1 {

    static Scanner reader = new Scanner(System.in);
    public static void main(String[] args) {
        int t = reader.nextInt();
        int[] answers = new int[t];
        for (int i = 0; i < t; i++) {
            answers[i] = solve();
        }
        for (int j = 0; j < t; j++) {
            System.out.println(answers[j]);
        }
    }

    static int solve() {
        int n = reader.nextInt();
        int[] nums = new int[n];
        int sum = 0;
        for (int i = 0; i < n; i++) {
            nums[i] = reader.nextInt();
            sum += nums[i];
        }
        ArrayList<Integer> modificationsList = new ArrayList<Integer>();
        if (sum == 0) {
            return 0;
        } else {
            for (int j = 1; j <= Math.sqrt(sum); j++) {
                if (sum % j == 0) {
                    int modifications = findModifications(sum / j, nums);
                    if (modifications >= 0) {
                        modificationsList.add(modifications);
                    }
                }
            }
        }
        return Collections.min(modificationsList); 
    }

    static int findModifications(int num, int[] nums) {
        int modifications = 0;
        int sum = nums[0]; 
        int k = 1; 
        while (k < nums.length) {
            if (sum == num) {
                if (k == nums.length - 1) {
                    break;
                } else {
                    sum = nums[k];
                    k++;
                }
            } else if (sum > num) {
                modifications = -1;
                break;
            } else {
                sum += nums[k];
                modifications++;
                k++;
            }
        }
        return modifications;
    }
}

I’m pretty sure the problem is in the function that finds the number of modifications, but I can’t tell how it goes wrong for certain inputs.

#2