[leetcode]Search a 2D Matrix

简单题。二分查找的应用。犯得错误是检查了数组下界0却忘了检查上界length。

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        // Start typing your Java solution below
        // DO NOT write main() function
        
        int m = matrix.length;
        if (m == 0) return false;
    	int n = matrix[0].length;
    	if (n == 0) return false;

    	if (target < matrix[0][0]) return false;
    	if (target > matrix[m-1][n-1]) return false;
    	
    	int left = 0; 
    	int right = m - 1;
    	while (left <= right) {
    		int mid = (left + right) / 2;
    		if (matrix[mid][0] == target) return true;
    		
    		if (matrix[mid][0] > target) {
    			right = mid - 1;
    		} else {
    			left = mid + 1;
    		}
    	}
    	
    	// at this time right < left
    	if (left < m && target > matrix[left][0]) {
    		return searchLine(matrix[left], target);
    	}
    	else if (right >= 0 && target > matrix[right][0]) {
    		return searchLine(matrix[right], target);
    	}
    	
    	return false;
    }  
    
    public boolean searchLine(int a[], int target)
    {
    	int left = 0; 
    	int right = a.length - 1;
    	while (left <= right) {
    		int mid = (left + right) / 2;
    		if (a[mid] == target) return true;
    		
    		if (a[mid] > target) {
    			right = mid - 1;
    		} else {
    			left = mid + 1;
    		}
    	}
    	return false;
    }
}