[LeetCode]Search a 2D Matrix II

最新推荐文章于 2022-08-05 12:18:43 发布

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本文介绍了一种高效的搜索算法，用于在一特殊性质的二维矩阵中查找指定值。该矩阵的每一行从左到右递增排序，并且每行的第一个元素大于前一行的最后一个元素。文章提供了一个具体的例子和C++实现代码。

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.

把二维矩阵变成一维来写binary search即可。

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int row = matrix.size();
        int col = matrix[0].size();
        int left = 0;
        int right = row*col-1;
        while(left<=right){//注意是小于等于
            int mid = (left+right)/2;
            int i = mid/col;
            int j = mid%col;
            if(matrix[i][j]==target){
                return true;
            }
            if(matrix[i][j]<target){
                left = mid+1 ;//important
            }
            else if(matrix[i][j]>target){
                right = mid-1; //important
            }
        }
        return false;
    }
};