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Search a 2D Matrix <leetcode>
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
.
思路:首先遍历每一行的首元素,找到目标如果存在,应该在哪一行,然后在行里进行搜索,本来在这里想用二分查找,但是直接扫了一遍也ac了,代码如下(没有进行优化):
1 class Solution { 2 public: 3 bool searchMatrix(vector<vector<int> > &matrix, int target) { 4 int index=0; 5 if(matrix.size()==0) 6 { 7 return false; 8 } 9 if(matrix.size()==1)10 {11 for(int i=0;i<matrix[0].size();i++)12 {13 if(target==matrix[0][i])14 {15 return true;16 }17 }18 return false;19 }20 for(int i=0;i<matrix.size();i++)21 {22 if(target>matrix[i][0])23 {24 index++;25 }26 else if(target==matrix[i][0])27 {28 return true;29 }30 }31 if(index==0) return false;32 for(int i=0;i<matrix[0].size();i++)33 {34 if(target==matrix[index-1][i])35 {36 return true;37 }38 }39 return false;40 41 }42 };
Search a 2D Matrix <leetcode>
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