[Leetcode] Search a 2D Matrix

Search a 2D Matrix

Write an efficient algorithm, searches for a value in a m x n Matrix. This matrix has the following properties:

• Integers in each row is sorted from the left to the right.
• The first integer of each row was greater than the last integer of the previous row.

For example,

Consider the following matrix:

[  [1,   3,  5,  7],  [Ten, One,],  [23, 30, 34, 50]]

Given target = 3 , return true .

Two-point lookup, Time complexity O (LOGM) +o (LOGN).

1 classSolution {2  Public:3     BOOLSearchmatrix (vector<vector<int>>& Matrix,inttarget) {4         if(matrix.size () = =0|| matrix[0].size () = =0)return false;5         intM=matrix.size (), n=matrix[0].size ();6         intleft=0, right=m-1;7          while(left<=Right )8         {9             intMid = (left+right)/2;Ten             if(matrix[mid][0]==target)return true; One             Else if(matrix[mid][0]<target) A             { -left = mid+1; -             } the             Else -             { -right = mid-1; -             } +         } -         intpos =Right ; +         if(pos<0)return false; Aleft=0; atright = N1; -          while(left<=Right ) -         { -             intMid = (left+right)/2; -             if(Matrix[pos][mid]==target)return true; -             Else if(matrix[pos][mid]<target) in             { -left = mid+1; to             } +             Else -             { theright = mid-1; *             } $         }Panax Notoginseng         return false; -     } the};

The problem can also be traversed from the upper right corner, with time complexity O (m) +o (n).

1 classSolution {2  Public:3     BOOLSearchmatrix (vector<vector<int>>& Matrix,inttarget) {4         if(matrix.size () = =0|| matrix[0].size () = =0)return false;5         intM=matrix.size (), n=matrix[0].size ();6         introw=0, col=n-1;7          while(Row<m && col>=0)8         {9             if(Matrix[row][col]==target)return true;Ten             Else if(Matrix[row][col]<target) row++; One             Elsecol--; A         } -         return false; -     } the};

[Leetcode] Search a 2D Matrix