开始刷leetcode day40： Search a 2D Matrix

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

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

For example,

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true.

Java:

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        int row = matrix.length;
        if(row==0) return false;
        int col = matrix[0].length;
        if(col==0) return false;
        int i=0;
        while(i<row)
        {
            if(target < matrix[i][0]) break;
            i++; 
        }
        if(i==0) return false;
        return findtarget(matrix[i-1], target, 0, col-1);
        
    }
    
    public boolean findtarget(int[] array, int target,int left, int right)
    {
        
        if(left > right) return false;
        int mid = (left+right)/2;
        if(array[mid] == target) return true;
        if(target < array[mid]) return findtarget(array,target, left, mid -1);
        if(target > array[mid]) return findtarget(array,target, mid+1, right);
        return false;
    }
}