Algorithms-LeetCode/000-099/074-Search-a-2D-Matrix.cpp at master · X-czh/Algorithms-LeetCode · GitHub

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// Time complexity: O(log(m) + log(n)) = O(log(mn))
// Space complexity: O(1)

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        if (matrix.empty() || matrix[0].empty()) return false;

        int row = -1;
        int lo = 0;
        int hi = matrix.size() - 1;
        while (lo <= hi) {
            int mid = lo + (hi - lo) / 2;
            if (matrix[mid][0] == target) {
                return true;
            } else if (matrix[mid][0] < target) {
                row = mid;
                lo = mid + 1;
            } else {
                hi = mid - 1;
            }
        }
        if (row == -1) return false;

        lo = 0;
        hi = matrix[0].size() - 1;
        while (lo <= hi) {
            int mid = lo + (hi - lo) / 2;
            if (matrix[row][mid] == target) {
                return true;
            } else if (matrix[row][mid] < target) {
                lo = mid + 1;
            } else {
                hi = mid - 1;
            }
        }
        return false;
    }
};