1351. 统计有序矩阵中的负数

暴力解法

class Solution {
public:
    int countNegatives(vector<vector<int>>& grid) 
    {
        int row = grid.size(),col = grid[0].size(),res = 0;
        for(int i = 0;i<row;i++)
        {
            for(int j= 0;j<col;j++)
            {
                if(grid[i][j]<0)
                    res ++;
            }
        }
        return res;
    }
};

二分算法

class Solution {
public:
    int countNegatives(vector<vector<int>>& grid) 
    {
        int left;
        int right;
        int mid;
        int count=0;
        for(int i=0;i<grid.size();i++)
        {
      
            left = 0;
            right = grid[0].size()-1;
            while(left <= right)
            {
               mid = (left+right)/2;
               if(grid[i][mid]<0)
               {
                 right = mid-1;
               }
               else
               {
                left = mid+1;
               }
            }
           count+=(grid[0].size()-left);
        }
        return count;
    }
};