[LeetCode] Search a 2D Matrix

iteye_8091

于 2013-05-03 16:13:39 发布

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本文介绍了一种在已排序的二维矩阵中高效查找特定值的算法。通过从右上角开始搜索，利用矩阵特性快速定位目标值，适用于数据结构与算法领域的学习者。

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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.

基础太渣！

class Solution {
public:
    bool searchMatrix(vector<vector<int> > &matrix, int target) {
        int h = matrix.size();
        if (h == 0) return false;
        int w = matrix[0].size();
        if (w == 0) return false;
        
        int r = 0, c = w - 1;
        while (r < h && c >= 0) {
            if (matrix[r][c] == target) return true;
            else if (matrix[r][c] > target) c--;
            else r++;
        }
        return false;
    }
};