标签：ble style ons const nis eof ack http namespace
题目链接：https://vjudge.net/problem/UVA-140
题解：这道题利用全排函数即可解决，但是这道题技巧性强，稍微不注意就会超时，一开始没有想起全排函数，自己写回溯全排超时了，主要问题出在：1、递归过程中疯狂判断最小带宽，循环太多了。2、处理原字符串的方法太LOW了。在借鉴了紫书思路的之后写出了AC代码如下：
AC代码：
#include<cstdio> #include<cstring> #include<algorithm> #include<vector> #define MAXN 30 using namespace std; typedef long long ll; vector<int> u; vector<int> v; int main(void){ char s[1000]; while(scanf("%s",s) == 1 && s[0] != ‘#‘){ u.clear(); v.clear(); int len = strlen(s); int p = 0,q = 0; int n = 0; int id[256]; char letter[MAXN]; for(char i = ‘A‘;i<=‘Z‘;i++){ if(strchr(s,i) != NULL){ id[i] = n++; letter[id[i]] = i; } } for(;;){ if(p<len && q < len){ while(1){ if(s[p] == ‘:‘){ break; } p++; if(p == len){ break; } } while(1){ if(s[q] == ‘;‘){ break; } q++; if(q == len){ break; } } for(int i = p+1;i<q;i++){ u.push_back(id[s[p - 1]]); v.push_back(id[s[i]]); } } else break; p++;q++; } int P[MAXN],BESTP[MAXN]; int pos[MAXN]; int best = n; for(int i = 0;i<n;i++){ P[i] = i; } do{ for(int i = 0;i<n;i++){ pos[P[i]] = i; } int bandwith = 0; for(int i = 0;i<u.size();i++){ bandwith = max(bandwith,abs(pos[u[i]]-pos[v[i]])); } if(bandwith < best){ best = bandwith; memcpy(BESTP,P,sizeof(P)); } }while(next_permutation(P,P+n)); for(int i = 0; i < n; i++) printf("%c ", letter[BESTP[i]]); printf("-> %d\n", best); } return 0; }
超时代码：
#include<cstdio> #include<cstring> #include<algorithm> #include<iostream> #include<string> #include<cmath> #define MAXN 30 using namespace std; typedef long long ll; int mmin; int maxalp; int nowMin; int graph[MAXN][MAXN]; int nowbox[MAXN]; int ansbox[MAXN]; void findNiceList(int cur){ if(cur - 1 == maxalp){ int ok = 1; int nowbig; int big1; int big = 0; for(int i =0;i<cur;i++){ big1 = 0; if(!ok){ break; } int nowchar = nowbox[i]; for(int j = 0;j<=maxalp;j++){ if(graph[nowchar][j] == 1){ nowbig = abs((find(nowbox,nowbox+cur,j) - nowbox) - i); if(nowbig > big1){ big1 = nowbig; } if(big1 >= mmin){ ok = 0; break; } } } if(big1 > big){ big = big1; } } nowMin = big; if(nowMin < mmin && ok){ for(int i = 0;i<=maxalp;i++){ ansbox[i] = nowbox[i]; mmin = nowMin; } } } else{ for(int i = 0;i<=maxalp;i++){ int ok = 1; for(int j = 0;j<cur;j++){ if(nowbox[j] == i){ ok = 0; break; } } if(ok){ nowbox[cur] = i; findNiceList(cur+1); } } } } /*void graphprint(void){ for(int i = 0;i<=maxalp;i++){ printf("%c:",‘A‘+i); for(int j = 0; j<MAXN;j++){ if(graph[i][j] == 1){ printf("%c ",j+‘A‘); } } printf("\n"); } }*/ int main(void){ string inistr; const string endstr = "#"; while((cin >> inistr) && inistr != endstr){ memset(graph,-1,sizeof(graph)); int len = inistr.size(); maxalp = -1; mmin = 99; nowMin = 0; for(int i = 0;i < len;i++){ if(inistr[i] <= ‘Z‘ && inistr[i] >=‘A‘){ if(inistr[i] - ‘A‘ > maxalp){ maxalp = inistr[i] - ‘A‘; } } if(i+1 == len || inistr[i+1] == ‘;‘){ int okindex; for(int m = i - 1;m>=0;m--){ if(inistr[m] == ‘:‘){ okindex = m; break; } } for(int m = okindex + 1;m<=i;m++){ graph[inistr[okindex - 1] - ‘A‘][inistr[m] - ‘A‘] = 1; graph[inistr[m] - ‘A‘][inistr[okindex - 1] - ‘A‘] = 1; } } } findNiceList(0); for(int i = 0;i<=maxalp;i++){ printf("%c ",ansbox[i] + ‘A‘); } printf("-> "); printf("%d\n",mmin); } return 0; }
标签：ble style ons const nis eof ack http namespace
原文地址：https://www.cnblogs.com/doubest/p/10175683.html
