[LeetCode] 74. Search a 2D Matrix

public class Solution {
//查找列
        public boolean binarySearchCol(int[][] matrix, int row, int target){
        int left=0,right=matrix[row].length-1;
        while(left<right){
            int mid=(left+right)/2;
            if(matrix[row][mid]==target)
                return true;
            if(matrix[row][mid]>target)
                right=mid-1;
            else 
                left=mid+1;
        }
        return matrix[row][left]==target;
    }
    public boolean searchMatrix(int[][] matrix, int target) {
        int m=matrix.length;
        if(m==0) return false;
        int n=matrix[0].length;
        if(n==0) return false;
        int left=0,right=m-1;
        /*注意这个二分查找要找到可能在的行，所以没有找到对应的target不能直接返回false，
        而要在最可能的一行单重继续查找*/
        while(left<right){
            int mid=(left+right+1)/2;
            if(matrix[mid][0]>target)
                right=mid-1;
            else if(matrix[mid][0]<target)
                left=mid;
            else return true;        
        }
       return  binarySearchCol(matrix, left,target);   
    }
}