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leetcode: Search a 2D Matrix

2024-07-02 14:09:09   228人阅读

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.

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

 


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