HDU 1501 Zipper

题意：给3个字符串，问第三个串能不能由前两个构成，在不改变相互顺序的情况下！

思路：记忆化搜索，开个hash数组保存，否则超时~

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1501

 

#include <cstdio>
#include <cstring>
#include <cmath>
#include <string>
#include <algorithm>
#include <iostream>
using namespace std ;
const int N=210;

char str1[N],str2[N],str[N*2];
bool hash[N][N];

int DP(int a,int b,int c){
    if(str[c]=='\0') return 1;
    if(hash[a][b]) return 0;
    hash[a][b]=1;
    if(str1[a]==str[c]&&DP(a+1,b,c+1)) return 1;
    if(str2[b]==str[c]&&DP(a,b+1,c+1)) return 1;
    return 0;
}

int main(){
 
//    freopen("data.in","r",stdin);
//    freopen("data.out","w",stdout); 
    
    int n,i;
    int iCase=1;
    while(scanf("%d",&n)!=EOF){
        scanf("%s %s %s",str1,str2,str);
        printf("Data set %d: ",iCase++);
        memset(hash,0,sizeof(hash));
        if(DP(0,0,0)) puts("yes");
        else puts("no"); 
    }
    return 0;
}

 

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <cmath>
 4 #include <string>
 5 #include <algorithm>
 6 #include <iostream>
 7 using namespace std ;
 8 const int N=210;
 9 
10 char str1[N],str2[N],str[N*2];
11 bool hash[N][N];
12 
13 int DP(int a,int b,int c){
14     if(str[c]=='\0') return 1;
15     if(hash[a][b]) return 0;
16     hash[a][b]=1;
17     if(str1[a]==str[c]&&DP(a+1,b,c+1)) return 1;
18     if(str2[b]==str[c]&&DP(a,b+1,c+1)) return 1;
19     return 0;
20 }
21 
22 int main(){
23  
24     freopen("data.in","r",stdin);
25     freopen("data.out","w",stdout); 
26     
27     int n,i;
28     int iCase=1;
29     while(scanf("%d",&n)!=EOF){
30         scanf("%s %s %s",str1,str2,str);
31         printf("Data set %d: ",iCase++);
32         memset(hash,0,sizeof(hash));
33         if(DP(0,0,0)) puts("yes");
34         else puts("no"); 
35     }
36     return 0;
37 }