M1760.袋子里最少数目的球

binary search, https://leetcode.cn/problems/minimum-limit-of-balls-in-a-bag/

思路：一开始的想法是将最多的一个袋子拆成 m + n 暴力回溯，显然太暴力了，后来看了题解，反向设置最终目标加二分法才是最合适的，用时约30分钟

class Solution 
{
public:
    int minimumSize(vector<int>& nums, int maxOperations) 
    {
        int left = 1, right = *max_element(nums.begin(), nums.end());
        int ans = 0;
        while (left <= right)
        {
            int mid = (right + left) / 2;
            long long op = 0;
            for(int x : nums)
            {
                op += (x - 1) / mid;
            }
            if (op <= maxOperations)
            {
                ans = mid;
                right = mid - 1;
            }
            else
                left = mid + 1;
        }
        return ans;
    }
};

二分答案

class Solution {
public:
    int minimumSize(vector<int>& nums, int maxOperations) {
        int l = 1, r = *max_element(nums.begin(), nums.end());
        int n = nums.size();
        while (l <= r) {
            int mid = l + (r - l) / 2;
            long long tmp = 0;
            for (int i = 0; i < n; i++) {
                tmp += (nums[i] / mid - 1);
                if (nums[i] % mid) tmp ++;
            }
            if (tmp <= maxOperations) r = mid - 1;
            else l = mid + 1;
        }
        return l;
    }
};