Title: Enter a string, arranged to print all of the characters in the string.
For example input string abc, the characters printed by a, b, c can be arranged out of all strings: abc, abc, bac, bca, cab, cba
We seek the entire string arrangement can be viewed as two steps: First, determine all possible character in the first position, i.e., all the characters in the first character and later exchange. A second step of fixing the first character, seeking arrange all of the following character. This time we still put all the characters back into two parts: The first character after character, and all characters after the character. Then one by one the first character and the characters following it ...... exchange
public void swap(char[] arr,int idx1,int idx2){
char temp = arr[idx1];
arr[idx1] = arr[idx2];
arr[idx2] = temp;
}
public void permutation(char[] arr,int index,int size){
if(index == size){
for(int i = 0;i<arr.length;i++){
System.out.print(arr[i]+ "");
}
System.out.println();
}
else{
for(int i = index;i<size;i++){
swap(arr,i,index); //我们从index向后扫描每一个字符（即指针i指向的字符），交换index和i指向的字符
permutation(arr,index+1,size); //对index后面的字符数组递归地做排列操作
swap(arr,i,index); //每次递归固定要排列字符数组第一个字符不变
}
}
} 