题解 | 牛群排列

class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param s string字符串
     * @return string字符串vector
     */
    vector<string> res;
    char tmp[11];
    int n;
    int vis[11]={0};
  //dfs的全排列模板
    void dfs(int x, string s) {
        if (x == n) {
            string str="";
            for(int i=0;i<n;i++)
            {
                str+=tmp[i];
            }
            res.push_back(str);
            return;
        }
        for (int i = 0; i < n; i++) {
            if (!vis[i]) {
                vis[i] = 1;
                tmp[x] = s[i];
                dfs(x + 1, s);
                vis[i] = 0;
            }
        }
    }
    vector<string> cowPermutations(string s) {
        // write code here
        n = s.size();
	  //首先冒泡排序 保持字典序
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                if (s[i] > s[j]) {
                    char str = s[i];
                    s[i] = s[j];
                    s[j] = str;
                }
            }
        }
        dfs(0, s);
        return res;
    }
};