[uva] 146 - ID Codes

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=82

老套路了, dfs + 剪枝. 我超时了好几次啊 失误,失误,忘记剪枝了.

//
//  main.cpp
//  uva146
//
//  Created by ello on 12/3/13.
//  Copyright (c) 2013 NextLife. All rights reserved.
//

#include <iostream>
#include <string>
#include <map>
#include <algorithm>
using namespace std;

string str;
string str2;
map<char, int> maps;

bool dfs(int cur) {
    if (cur == str2.size()) {
        if (str2 <= str) {
            return false;
        }
        return true;
    }
    map<char, int>::iterator it;
    for (it = maps.begin(); it != maps.end(); it++) {
        long num = count(str2.begin(), str2.begin() + cur, (*it).first);
        if ((*it).second > num) {
            str2[cur] = (*it).first;
//            cout<<cur<<','<<str2<<endl;
            if (str2.substr(0, cur + 1) < str.substr(0, cur + 1) || !dfs(cur + 1)) {
                continue;
            } else {
                return true;
            }
        }
    }
    return false;
}

int main(int argc, const char * argv[])
{
    while (getline(cin, str)) {
        
        if (str == "#") {
            break;
        }
        maps.clear();
        for (unsigned int i = 0; i < str.size(); ++i) {
            maps[str[i]] += 1;
        }
        str2 = str;
        bool flag = false;
        for (unsigned int i = 1; i < str2.size(); ++i) {
            if (str2[i] > str2[i - 1]) {
                flag = true;
                break;
            }
        }
        if (flag && dfs(0)) {
            cout<<str2<<endl;
        } else {
            cout<<"No Successor"<<endl;
        }
    }
    return 0;
}