URAL 1501. Sense of Beauty(记忆化搜索)

题目链接

本来暴力写个TLE了，加上记忆化就A了。

 #include <cstring>
 #include <cstdio>
 #include <string>
 #include <iostream>
 #include <algorithm>
 #include <cmath>
 using namespace std;
 int pre[][];
 int flag[][];
 char s1[],s2[];
 int sum1[],sum2[];
 int n;
 int que[];
 int dfs(int x,int y)
 {
     if(x == n&&y == n)
     return ;
     if(flag[x][y] == )
     return ;
     else if(flag[x][y] == )
     return ;
     if(x+ <= n)
     {
         if(abs(sum1[x+] + sum2[y]-(x++y-sum1[x+]-sum2[y])) <= )
         {
             pre[x+][y] = ;
             if(dfs(x+,y))
             return flag[x+][y] = ;
             else
             {
                 flag[x+][y] = ;
                 pre[x+][y] = ;
             }
         }
     }
     if(y+ <= n)
     {
         if(abs(sum1[x] + sum2[y+]-(x+y+-sum1[x]-sum2[y+])) <= )
         {
             pre[x][y+] = ;
             if(dfs(x,y+))
             return flag[x][y+] = ;
             else
             {
                 flag[x][y+] = ;
                 pre[x][y+] = ;
             }
         }
     }
     return ;
 }
 int main()
 {
     int i,x,y;
     scanf("%d%s%s",&n,s1,s2);
     if(s1[] == '')
     sum1[] = ;
     if(s2[] == '')
     sum2[] = ;
     for(i = ;i <= n;i ++)
     {
         if(s1[i-] == '')
         sum1[i] = sum1[i-] + ;
         else
         sum1[i] = sum1[i-];
         if(s2[i-] == '')
         sum2[i] = sum2[i-] + ;
         else
         sum2[i] = sum2[i-];
     }
     if(dfs(,))
     {
         x = n;
         y = n;
         int m = ;
         while(x != ||y != )
         {
             que[m++] = pre[x][y];
             if(pre[x][y] == )
             x --;
             else
             y --;
         }
         for(i = m-;i >= ;i --)
         printf("%d",que[i]);
         printf("\n");
     }
     else
     printf("Impossible\n");
     return ;
 }