Today I have done leetcode's July LeetCoding Challenge with cpp.

July LeetCoding Challenge 24

Description

Search a 2D Matrix II

Write an efficient algorithm that searches for a value target in an m x n integer matrix 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 1:

Input: 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]], target = 5
Output: true

Example 2:

Input: 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]], target = 20
Output: false

Constraints:

• m == matrix.length
• n == matrix[i].length
• 1 <= n, m <= 300
• -10^9 <= matrix[i][j] <= 10^9
• All the integers in each row are sorted in ascending order.
• All the integers in each column are sorted in ascending order.
• -10^9 <= target <= 10^9

Solution

class Solution {
public:
  bool searchMatrix(vector<vector<int>>& matrix, int target) {
    int rows = matrix.size();
    int cols = matrix.front().size();
    int row = 0;
    int col = cols - 1;
    while(row < rows && col >= 0) {
      if(matrix[row][col] == target) return true;
      if(matrix[row][col] > target) {
        col -= 1;
      } else {
        row += 1;
      }
    }
    return false;
  }
};

// Accepted
// 129/129 cases passed (184 ms)
// Your runtime beats 45.36 % of cpp submissions
// Your memory usage beats 21.86 % of cpp submissions (15 MB)