1.6打印字符串排列

public static void swapChar(char[] str ,int i,int j){
        char tmp = str[i];
        str[i] = str[j];
        str[j] = tmp;
    }
    public static void printString(char[] str,int low,int high){
        int i;
        char tmp;
        if(low == high){
            System.out.println(str);
        }else{
            for(i=low;i<high;i++ ){
                swapChar(str,low,i);
                printString(str,low+1,high);
                swapChar(str,low,i);
            }
        }
    }

对递归的理解，这里的字符串没有重复字符。