HDU_3183_A Magic Lamp
2018-06-17 21:48:01来源:未知 阅读 ()
A Magic Lamp
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4694 Accepted Submission(s): 1947
The question is: give you an integer, you are allowed to delete exactly m digits. The left digits will form a new integer. You should make it minimum.
You are not allowed to change the order of the digits. Now can you help Kiki to realize her dream?
Each test case will contain an integer you are given (which may at most contains 1000 digits.) and the integer m (if the integer contains n digits, m will not bigger then n). The given integer will not contain leading zero.
If the result contains leading zero, ignore it.
- 长度为n的数串去掉m个数问剩下的数的最小值是多少
- 等价于求长度为n的数挑(n-m)个数使得其值最小
- 那么我们只要从高位开始每次挑选最小数一共挑(n-m)个就是结果
- 用ST表计算区间min
- 注意前导零的处理
1 #include <iostream> 2 #include <string> 3 #include <cstdio> 4 #include <cstring> 5 #include <algorithm> 6 #include <climits> 7 #include <cmath> 8 #include <vector> 9 #include <queue> 10 #include <stack> 11 #include <set> 12 #include <map> 13 using namespace std; 14 typedef long long LL ; 15 typedef unsigned long long ULL ; 16 const int maxn = 1e3 + 10 ; 17 const int inf = 0x3f3f3f3f ; 18 const int npos = -1 ; 19 const int mod = 1e9 + 7 ; 20 const int mxx = 100 + 5 ; 21 const double eps = 1e-6 ; 22 const double PI = acos(-1.0) ; 23 24 int n, m, fac[10], dp[maxn][10], l, r, p, ans[maxn], tot, rec; 25 char str[maxn]; 26 int main(){ 27 // freopen("in.txt","r",stdin); 28 // freopen("out.txt","w",stdout); 29 for(int i=0;i<10;i++) 30 fac[i]=(1<<i); 31 while(~scanf("%s %d",str+1,&m)){ 32 n=strlen(str+1); 33 m=n-m; 34 rec=m; 35 int k=(int)(log((double)n)/log(2.0)); 36 for(int i=1;i<=n;i++) 37 dp[i][0]=i; 38 for(int j=1;j<=k;j++) 39 for(int i=1;i+fac[j]-1<=n;i++){ 40 int pl=dp[i][j-1], pr=dp[i+fac[j-1]][j-1]; 41 if(str[pl]<=str[pr]) 42 dp[i][j]=pl; 43 else 44 dp[i][j]=pr; 45 } 46 l=1; 47 tot=0; 48 while(m){ 49 r=n-m+1; 50 k=(int)(log((double)(r-l+1))/log(2.0)); 51 int pl=dp[l][k], pr=dp[r-fac[k]+1][k]; 52 if(str[pl]<=str[pr]) 53 p=pl; 54 else 55 p=pr; 56 ans[tot++]=p; 57 l=p+1; 58 m--; 59 } 60 int flag=0; 61 for(int i=0;i<tot;i++){ 62 if(!(str[dp[ans[i]][0]]-'0')){ 63 if(flag) 64 printf("%c",str[ans[i]]); 65 }else{ 66 flag=1; 67 printf("%c",str[ans[i]]); 68 } 69 } 70 if(!flag) 71 printf("0"); 72 cout<<endl; 73 } 74 return 0; 75 }
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