二分

class Solution {
public:
    bool searchArray(vector<vector<int>> array, int target) {
        int n = array.size();
        if(n == 0)   return false;
        int m = array[0].size();
        for(int i = 0; i < n; i ++ ){
            int l = 0, r = m - 1;
            while(l < r){
                int mid = l + r >> 1;
                if(array[i][mid] >= target)     r = mid;
                else    l = mid + 1;
            }
            if(array[i][l] == target)   return true;
        }
        return false;
    }
};