列出九宫格输入组合

题目：列出九宫格键盘输入的所有字母组合

思路：将字母的组合看成k进制的数，列出字母组合的过程即为对数进行加法运算。

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#include <stdio.h> #include <string.h> #include <stdlib.h>   char* letter[] = {"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};   void listAll(char* input) {     int len = strlen(input);     int total = 1;     int i;     for ( i=0; i<len; i++)     {         total = total*strlen(letter[input[i]-'0']);     }       for( i=0; i<total; i++)     {         //char item[4];         char* item = (char*)malloc(len+1);         int j;         for( j=0; j<len; j++)         {             int size = strlen(letter[input[j]-'0']);             int num = i;             int index = num%size;             num = num/size;             item[j] = letter[input[j]-'0'][index];          }         item[j] = '\0';         printf("%s\n",item);               } }   int main() {     char* input = "025";     listAll(input);       return 0; }