poj1256Anagram（全排列& tolower）

tolower

头文件：#include<iostream>定义函数:int tolower(int c)函数说明：若参数c为大写字母，则将其对应的小写字母返回返回值：返回转换后的小写字母，若不须转换则将参数c值返回

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poj1256Anagram

Description

You are to write a program that has to generate all possible words
from a given set of letters. Example: Given the word “abc”, your
program should - by exploring all different combination of the three
letters - output the words “abc”, “acb”, “bac”, “bca”, “cab” and
“cba”. In the word taken from the input file, some letters may appear
more than once. For a given word, your program should not produce the
same word more than once, and the words should be output in
alphabetically ascending order.

Input

The input consists of several words. The first line contains a number
giving the number of words to follow. Each following line contains one
word. A word consists of uppercase or lowercase letters from A to Z.
Uppercase and lowercase letters are to be considered different. The
length of each word is less than 13.

Output

For each word in the input, the output should contain all different
words that can be generated with the letters of the given word. The
words generated from the same input word should be output in
alphabetically ascending order. An upper case letter goes before the
corresponding lower case letter.

Sample Input

3aAbabcacba

Sample Output

AabAbaaAbabAbAabaAabcacbbacbcacabcbaaabcaacbabacabcaacabacbabaacbacabcaacaabcabacbaa

Hint

An upper case letter goes before the corresponding lower case letter.
So the right order of letters is ‘A’<’a’<’B’<’b’<…<’Z’<’z’.

代码：

#include <algorithm>#include <stdio.h>#include <iostream>using namespace std;bool cmp(char a,char b){    if(tolower(a)==tolower(b))        return a<b;//如果两个字母转化成小写字母一样，ASCII值小的前面，也就是大写字母在前面    else return tolower(a)<tolower(b);}int main(){    int t;    scanf("%d",&t);    string s;    while(t--)    {        cin>>s;        sort(s.begin(),s.end(),cmp);        do        {            cout<<s<<endl;        }while(next_permutation(s.begin(),s.end(),cmp));    }}

next_permutation详解