ITSA 51 - [Problem 5] Number Puzzle - 參考答案

Difficulty: Easy
Ref: ITSA 51 - [Problem 5] Number Puzzle

/*******************************************************/
/* [Problem 5] Number Puzzle                           */
/* Author: awei0905  [at]  awei0905.blogspot.tw        */
/* Version: 2017/05/28                                 */
/*******************************************************/
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>

char buf[3][4];
int ok = 0;
void permute(int *a, int l, int r)
{
 if (ok) return;
 if (l == r) {     
  int num3 = a[buf[2][0]] * 100 + a[buf[2][1]] * 10 + a[buf[2][2]];
  if (num3 >= 300) return;
  int num1 = a[buf[0][0]] * 10 + a[buf[0][1]];
  int num2 = a[buf[1][0]] * 10 + a[buf[1][1]];
  if (num1 + num2 == num3) ok = 1;
 }
 else
 {
  char temp;
  for (int i = l; i <= r; i++)
  {
   temp = *(a + l);
   *(a + l) = *(a + i);
   *(a + i) = temp;
   permute(a, l + 1, r);
   temp = *(a + l);
   *(a + l) = *(a + i);
   *(a + i) = temp;
  }
 }
}

int main()
{
 while (scanf("%s%s%s", buf[0], buf[1], buf[2]) != EOF) {
  for (int i = 0; i < 3; i++)
   for (int j = 0; buf[i][j] != '\0'; j++)
    buf[i][j] -= 'A';

  ok = 0;
  int str[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
  permute(str, 0, 9);
  if (ok)
   printf("YES\n");
  else
   printf("NO\n");
 }
 return 0;
}

Debug： I/O
窮舉法，把所有可能的答案進行排列匹配。

AB
BC
EED
AA
BB
ABA
AB
CD
DFG
AB
CD
EFG
AB
CD
CAD

YES
NO
YES
YES
NO