题目描述
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.
Example 1:
Input:
matrix = [
[1, 3, 5, 7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]
target = 3
Output: true
Example 2:
Input:
matrix = [
[1, 3, 5, 7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]
target = 13
Output: false
思路
从左下角开始搜索,每次可以分到小于的范围或者大于的范围。
代码
class Solution {
public:
bool searchMatrix(vector<vector<int>>& matrix, int target) {
if (matrix.empty()) return false;
int n = matrix.size();
int m = matrix[0].size();
int row = n-1;
int col = 0;
while(row >= 0 && col <= m-1) {
if (matrix[row][col] == target) return true;
else if (matrix[row][col] < target) col++;
else if (matrix[row][col] > target) row--;
}
return false;
}
};
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