Delete Columns to Make Sorted

给一个数组, 里面是同样长度的string, 求这个string组成的grid是否对应的每列都是字典序的

class Solution {
public:
    int minDeletionSize(vector<string>& strs) {
        int n = strs.size();
        int m = strs[0].length();
        int res = 0;
        for(int i = 0; i < m; i++){
            for(int j = 1; j < n; j++) {
                if(strs[j - 1][i] > strs[j][i]){
                    res++;
                    break;
                }
            }
        }
        return res;
    }
};