AOJ0033_Bit01.cpp

#include <iostream>
using namespace std;
 
int main() {
    int n, balls[10]; cin >> n;
    while(n--){
        for(int i = 0; i < 10; i++) cin >> balls[i];
         
        bool sortable = false;
        for(int i = 0; i < (1 << 10); i++){
            int bit = i;
            bool ok = true;
             
            int top[2] = {0,0}; //top[0]: B, top[1]: C
            for(int j = 0; j < 10; j++){
                if(top[bit & 1] > balls[j]){
                    ok = false; break;
                }
                top[bit & 1] = balls[j];
                bit >>= 1;
            }
             
            if(ok) {
                sortable = true; break;
            }
        }
        cout << (sortable ? "YES" : "NO") << endl;
    }
}

AOJ0033_DFS01.cpp

#include <iostream>
using namespace std;
  
int balls[10]; // 玉の順序を記録
  
bool dfs(int idx, int b, int c){ 
    if(idx > 9) return true;
      
    bool ok = false;
    if(b < balls[idx]){
          ok = dfs(idx+1, balls[idx], c); // 筒Bに入れられるとき
    }
    if(c < balls[idx]){
          ok = dfs(idx+1, b, balls[idx]); // 筒Cに入れられるとき
    }
    return ok;
}
  
int main() {
    int n; cin >> n; // データセットの数
    while(n--){
        for(int i = 0; i < 10; i++) cin >> balls[i];
        cout << (dfs(0, 0, 0) ? "YES" : "NO") << endl;
    }
}

AOJ0033_DFS02.cpp

#include <iostream>
#include <stack>
#include <tuple>
using namespace std;
 
int main() {
    int n; cin >> n;
    while(n--){
        int balls[10];
        for(int i = 0; i < 10; i++) cin >> balls[i];
         
        enum {IDX, B, C};
        stack<tuple<int, int, int> > states;

        bool sortable = false;
        states.push(make_tuple(0,0,0));
        while(!states.empty()){
            tuple<int, int, int> now = states.top();
            states.pop();

            int idx = get<IDX>(now);
            if(idx < 10){
                if(get<B>(now) < balls[idx]){
                    if(idx == 9){
                        sortable = true; break;
                    }
                    states.push(make_tuple(idx+1,balls[idx],get<C>(now)));
                }
                if(get<C>(now) < balls[idx]){
                    if(idx == 9){
                        sortable = true; break;
                    }
                    states.push(make_tuple(idx+1,get<B>(now),balls[idx]));
                }
            }
        }
        cout << (sortable ? "YES" : "NO") << endl;
    }
}

AOJ0033_greedy01.cpp

#include <iostream>
using namespace std;

int main() {
    int n; cin >> n;  // データセットの数
    while(n--){
        int balls[10] = {0};
        for(int i = 0; i < 10; i++) cin >> balls[i]; // 各データセットの入力
        
        bool isYES = true;  // 玉10個を振り分けられるかどうか
        int topB = 0, topC = 0;  // 筒B及び筒Cの最上部の玉の値
        for(int i = 0; i < 10; i++){
            if (topB < balls[i]){
                topB = balls[i];
            } else if (topC < balls[i]) {
                topC = balls[i];
            } else {
                isYES = false;
                break;
            }
        }
        cout << (isYES ? "YES" : "NO") << endl;
    }
}