Python O(m+n) with clear search strategy
\n\n    class Solution:\n        # @param {integer[][]} matrix\n        # @param {integer} target\n        # @return {boolean}\n        def searchMatrix(self, m
\n\n    class Solution:\n        # @param {integer[][]} matrix\n        # @param {integer} target\n        # @return {boolean}\n        def searchMatrix(self, matrix, target):\n            if matrix:\n                row,col,width=len(matrix)-1,0,len(matrix[0])\n                while row>=0 and col<width:\n                    if matrix[row][col]==target:\n                        return True\n                    elif matrix[row][col]>target:\n                        row=row-1\n                    else:\n                        col=col+1\n                return False
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