Search a 2D Matrix

Write an efficient algorithm that searches for a value in an mx 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.

Example

Consider the following matrix:

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

Given target = 3, return true.

来源： http://www.lintcode.com/en/problem/search-a-2d-matrix/#

分析

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首先想到的是将二维坐标转换为一维

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public class Solution {     /**      * @param matrix, a list of lists of integers      * @param target, an integer      * @return a boolean, indicate whether matrix contains target      */     public boolean searchMatrix(int[][] matrix, int target) {         // write your code here         if(matrix == null || matrix.length == 0 || matrix[0].length == 0) return false;         int row = matrix.length;         int col = matrix[0].length;                   int left = 0, right = row * col - 1;         while(left < right){             int mid = left + (right - left) / 2;             int i = mid / col;             int j = mid % col;             if(matrix[i][j] < target){                 left = mid + 1;             }             else{                 right = mid;             }         }         if(matrix[left / col][left % col] == target)             return true;         else             return false;     } }

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