文章目录

• • 原题题目
  • 代码实现（首刷超时 TLE 50/85 dp）
  • 代码实现（首刷看了点思路点拨后 二分自解）

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原题题目

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代码实现（首刷超时 TLE 50/85 dp）

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class Solution {
public:
    int shipWithinDays(vector<int>& weights, int days) {
        vector<vector<int>> dp(weights.size(),vector<int>(weights.size(),0));
        for(int i=0;i<weights.size();++i)
        {
            for(int j=i;j<weights.size();++j)
            {
                if(i == j)  dp[i][j] = weights[j];
                else    dp[i][j] = dp[i][j-1] + weights[j];
            }
        }

        vector<int> now_min(weights.size(),0),pre_min(now_min),tmp_zero(pre_min);
        vector<bool> now_visit(weights.size(),false),pre_visit(now_visit),tmp_false(now_visit);
        int ret = INT_MAX;
        for(int i=0;i<days;++i)
        {
            now_visit = tmp_false;
            now_min = tmp_zero;
            for(int start=i;start<weights.size();++start)
            {
                if(start && !pre_visit[start-1])  continue;
                for(int end=start;end<weights.size();++end)
                {
                    now_visit[end] = true;
                    if(!start)
                    {
                        now_min[end] = dp[start][end];
                        continue;
                    }
                    if(!now_min[end]) now_min[end] = max(pre_min[start-1],dp[start][end]);
                    else  now_min[end] = min(now_min[end],max(pre_min[start-1],dp[start][end]));
                }
            }
            pre_visit = now_visit;
            pre_min = now_min;
            if(pre_visit.back())    ret = min(ret,pre_min.back());
        }
        
        return ret;
    }
};

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代码实现（首刷看了点思路点拨后 二分自解）

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class Solution {
public:
    int shipWithinDays(vector<int>& weights, int days) {
        int left = 0,right = 0,sum = 0;
        for(const auto& num:weights)
        {
            left = max(left,num);
            right += num;
        }
        sum = right;

        while(left < right)
        {
            int mid = (left + right)/2;
            int tmpsum = 0;
            int day = 1,pos = 0;
            while(day <= days && pos < weights.size())
            {
                if(tmpsum + weights[pos] > mid)
                {
                    tmpsum = 0;
                    ++day;
                }
                else
                    tmpsum += weights[pos++];
            }
            if(day > days) left = mid+1;
            else    right = mid;
        }
        return left;
    }
};