SRM 394(1-250pt)

DIV1 250pt

题意：给定一个字符串s('a'-'z')，计其中出现次数最多和最少的字母分别出现c1次和c2次，若在s中去掉最多k个字母，求去掉以后c1 - c2的最小值。

解法：做题的时候，想到了用dfs暴力枚举，然后TLE了。然后想到了枚举c2，求c1的最小值，最后写了比较麻烦的代码，过了。然后看了题解才发现，枚举c1和c2。。。。。

　　　真的是看到'a' - 'z'就应该想到这种方法。。。。

tag:think, brute-force

 // BEGIN CUT HERE
 /*
  * Author:  plum rain
  * score :
  */
 /*

  */
 // END CUT HERE
 #line 11 "RoughStrings.cpp"
 #include <sstream>
 #include <stdexcept>
 #include <functional>
 #include <iomanip>
 #include <numeric>
 #include <fstream>
 #include <cctype>
 #include <iostream>
 #include <cstdio>
 #include <vector>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 #include <cstdlib>
 #include <set>
 #include <queue>
 #include <bitset>
 #include <list>
 #include <string>
 #include <utility>
 #include <map>
 #include <ctime>
 #include <stack>

 using namespace std;

 #define clr0(x) memset(x, 0, sizeof(x))
 #define clr1(x) memset(x, -1, sizeof(x))
 #define pb push_back
 #define mp make_pair
 #define sz(v) ((int)(v).size())
 #define all(t) t.begin(),t.end()
 #define zero(x) (((x)>0?(x):-(x))<eps)
 #define out(x) cout<<#x<<":"<<(x)<<endl
 #define tst(a) cout<<a<<" "
 #define tst1(a) cout<<#a<<endl
 #define CINBEQUICKER std::ios::sync_with_stdio(false)

 typedef vector<int> VI;
 typedef vector<string> VS;
 typedef vector<double> VD;
 typedef pair<int, int> pii;
 typedef long long int64;

 const double eps = 1e-;
 const double PI = atan(1.0)*;
 const int inf =  / ;

 int num[], n2[], n1[];
 int idx[], all;
 pii an[];

 int gao(int k)
 {
     clr0 (n2);
     for (int i = ; i < ; ++ i)
         ++ n2[num[i]];
     int pos = ;
     while (!n2[pos]) -- pos;
     while (k > ){
         if (pos < ) return ;
         k -= n2[pos];
         n2[pos-] += n2[pos];
         n2[pos--] = ;
     }
     if (!k) return pos;
     return pos + ;
 }

 class RoughStrings
 {
     public:
         int minRoughness(string s, int k){
             clr0 (num);
             for (int i = ; i < sz(s); ++ i)
                 ++ num[s[i] - 'a'];
             all = ;
             for (int i = ; i < ; ++ i)
                 if (num[i]) n1[all++] = num[i];
             if (all == ) return ;
             sort(n1, n1+all);
             int ans = max(gao(k) - n1[], ), use = ;
             for (int i = ; i < all; ++ i){
                 use += n1[i];
                 if (k < use) break;
                 if (i == all-) ans = ;
                 else ans = min(ans, max(gao(k-use) - n1[i+], ));
             }
             return ans;
         }

 // BEGIN CUT HERE
     public:
     void run_test(int Case) { if ((Case == -) || (Case == )) test_case_0(); if ((Case == -) || (Case == )) test_case_1(); if ((Case == -) || (Case == )) test_case_2(); if ((Case == -) || (Case == )) test_case_3(); if ((Case == -) || (Case == )) test_case_4(); if ((Case == -) || (Case == )) test_case_5(); }
     private:
     template <typename T> string print_array(const vector<T> &V) { ostringstream os; os << "{ "; for (typename vector<T>::const_iterator iter = V.begin(); iter != V.end(); ++iter) os << '\"' << *iter << "\","; os << " }"; return os.str(); }
     void verify_case(int Case, const int &Expected, const int &Received) { cerr << "Test Case #" << Case << "..."; if (Expected == Received) cerr << "PASSED" << endl; else { cerr << "FAILED" << endl; cerr << "\tExpected: \"" << Expected << '\"' << endl; cerr << "\tReceived: \"" << Received << '\"' << endl; } }
     void test_case_0() { string Arg0 = "aaaaabbc"; int Arg1 = ; int Arg2 = ; verify_case(, Arg2, minRoughness(Arg0, Arg1)); }
     void test_case_1() { string Arg0 = "aaaabbbbc"; int Arg1 = ; int Arg2 = ; verify_case(, Arg2, minRoughness(Arg0, Arg1)); }
     void test_case_2() { string Arg0 = "veryeviltestcase"; int Arg1 = ; int Arg2 = ; verify_case(, Arg2, minRoughness(Arg0, Arg1)); }
     void test_case_3() { string Arg0 = "gggggggooooooodddddddllllllluuuuuuuccckkk"; int Arg1 = ; int Arg2 = ; verify_case(, Arg2, minRoughness(Arg0, Arg1)); }
     void test_case_4() { string Arg0 = "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"; int Arg1 = ; int Arg2 = ; verify_case(, Arg2, minRoughness(Arg0, Arg1)); }
     void test_case_5() { string Arg0 = "bbbccca"; int Arg1 = ; int Arg2 = ; verify_case(, Arg2, minRoughness(Arg0, Arg1)); }

 // END CUT HERE

 };

 // BEGIN CUT HERE
 int main()
 {
 //    freopen( "a.out" , "w" , stdout );
     RoughStrings ___test;
     ___test.run_test(-);
        return ;
 }
 // END CUT HERE

网上看到的代码：