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Search a 2D Matrix

Problem​

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 from left to right.
  • The first integer of each row is greater than the last integer of the previous row.

Solution Approach​

Click - to see solution code
class Solution {
   public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int n = matrix.size();
        int start = 0, end = n - 1;
        int mid, indx = 0;

        while (start <= end) {
            mid = (start + end) / 2;
            if (matrix[mid][0] > target) {
                end = mid - 1;
            } else {
                indx = mid;
                start = mid + 1;
            }
        }

        start = 0, end = matrix[0].size() - 1;
        int i = 0;
        while (start <= end) {
            mid = (start + end) / 2;
            if (matrix[indx][mid] > target) {
                end = mid - 1;
            } else {
                i = mid;
                start = mid + 1;
            }
        }
        if (matrix[indx][i] == target) return true;
        return false;
    }
};