74. Search a 2D Matrix

Posted 2022-01-31 reboot329

刷
June-21-2019

这个居然也没记过？

二维转一维，用的究极二分大法，但是如果因为超左右边界而找不到。

[[2,3,5,7],[10,11,16,20],[23,30,34,50]]  
51

yes left, no right => 找不到的话L是停在最右边超过的地方，最后判断会out of boundary..

    public boolean searchMatrix(int[][] matrix, int target) 
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) return false;
        
        int row = matrix.length;
        int col = matrix[0].length;
        if (target < matrix[0][0] || target > matrix[row - 1][col - 1]) return false;
        int l = 0, r = row * col - 1;
        
        while (l <= r) 
            int m = l + (r - l) / 2;
            int val = matrix[m / col][m % col];
            
            if (val == target) 
                r = m - 1;
             else if (val < target) 
                l = m + 1;
             else 
                r = m - 1;
            
        
        
        return matrix[l / col][l % col] == target;