LeetCode [240] Search a 2D Matrix II

 240. Search a 2D Matrix II

Medium

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 in ascending from left to right.
• Integers in each column are sorted in ascending from top to bottom.

Example:

Consider the following matrix:

[
  [1,   4,  7, 11, 15],
  [2,   5,  8, 12, 19],
  [3,   6,  9, 16, 22],
  [10, 13, 14, 17, 24],
  [18, 21, 23, 26, 30]
]

Given target = 5, return true.

Given target = 20, return false.

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