diff --git a/HDOJ/5920_dgutfly.cpp b/HDOJ/5920_dgutfly.cpp
new file mode 100644
index 0000000..469804f
--- /dev/null
+++ b/HDOJ/5920_dgutfly.cpp
@@ -0,0 +1,70 @@
+#include <iostream>
+#include <cstdio>
+#include <cstring>
+#include <cmath>
+#include <algorithm>
+#include <string>
+#include <cstdlib>
+#include <vector>
+#include <set>
+#include <map>
+using namespace std;
+const double eps=1e-8;
+int len;
+//大数乘法
+void subtract(char *a,char *b,char *c)
+{
+    for(int i=len-1;i>=0;i--)
+    {
+        c[i]=a[i]-b[i]+'0';
+        if(c[i]<'0')c[i]+=10,a[i-1]--;
+    }
+}
+
+char str[2][1005],sub[50][1005];
+int main()
+{
+    int i,j,k,n;
+    scanf("%d",&n);getchar();
+    for(int h=1;h<=n;h++)
+    {
+        memset(sub,'0',sizeof(sub));
+        gets(str[0]);
+        len=strlen(str[0]);
+        int old=1,now=0;
+        int cnt=0;
+        for(i=0;str[now][i];)//前置0到末尾，整个数就是0
+        {
+            old^=1,now^=1;//滚动数组
+            if(!strcmp(str[old]+i,"10"))//10=9+1
+            {
+                sub[cnt][0]='9';sub[cnt][1]=0;cnt++;
+                sub[cnt][0]='1';sub[cnt][1]=0;cnt++;
+                break;
+            }
+            for(j=i;j<=len-1-j+i && str[old][j]<=str[old][len-1-j+i];j++);
+            strcpy(sub[cnt],str[old]);
+            if(j<len-1-j+i)//对折后有小于的，就只能取较小的回文数
+            {
+                sub[cnt][(i+len-1)/2]--;
+                for(j=(i+len-1)/2;j>=0 && sub[cnt][j]<'0';j--)sub[cnt][j]+=10,sub[cnt][j-1]--;
+            }
+            for(j=0;sub[cnt][j]=='0';j++);//去前导0
+            for(k=j;k<=len-1-k+j;k++)sub[cnt][len-1-k+j]=sub[cnt][k];//根据前半串对折构造后半串
+            sub[cnt][len]=0;
+            subtract(str[old],sub[cnt],str[now]);
+            for(;str[now][i]=='0';i++);
+            cnt++;
+        }
+        printf("Case #%d:\n%d\n",h,cnt);
+        for(i=0;i<cnt;i++)
+        {
+            char *s;
+            for(s=sub[i];*s=='0';s++);
+            puts(s);
+        }
+    }
+    return 0;
+}
+
+ugly problem