【HDOJ】3325 Arithmetically Challenged

简单DFS。

/* 3325 */
#include <iostream>
#include <set>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

#define MAXN 100005
#define INF 0x3f3f3f3f

int buf[MAXN];
int a[4];
set<int> S;
set<int>::iterator iter;

int cal(int a, int b, int op) {
    if (op == 0)    return a+b;
    if (op == 1)    return a-b;
    if (op == 2)    return a*b;
    if (op == 3)    return (b==0||a%b) ? INF:a/b;
    return INF;
}

void f() {
    int i, j, k;
    int tmp1, tmp2;
    int ans;
    
    //((AB)C)D (AB) (CD)
    for (i=0; i<4; ++i) {
        tmp1 = cal(a[0], a[1], i);
        if (tmp1 == INF)
            continue;
        for (j=0; j<4; ++j) {
            tmp2 = cal(tmp1, a[2], j);
            if (tmp2 != INF) {
                for (k=0; k<4; ++k) {
                    ans = cal(tmp2, a[3], k);
                    if (ans != INF)
                        S.insert(ans);
                }
            }
            tmp2 = cal(a[2], a[3], j);
            if (tmp2 != INF) {
                for (k=0; k<4; ++k) {
                    ans = cal(tmp1, tmp2, k);
                    if (ans != INF)
                        S.insert(ans);
                }
            }
        }
    }
    
    // (A(BC))D A((BC)D)
    for (i=0; i<4; ++i) {
        tmp1 = cal(a[1], a[2], i);
        if (tmp1 == INF)
            continue;
        for (j=0; j<4; ++j) {
            tmp2 = cal(a[0], tmp1, j);
            if (tmp2 != INF) {
                for (k=0; k<4; ++k) {
                    ans = cal(tmp2, a[3], k);
                    if (ans != INF)
                        S.insert(ans);
                }
            }
            tmp2 = cal(tmp1, a[3], j);
            if (tmp2 != INF) {
                for (k=0; k<4; ++k) {
                    ans = cal(a[0], tmp2, k);
                    if (ans != INF)
                        S.insert(ans);
                }
            }
        }
    }
    
    // A(B(CD))
    for (i=0; i<4; ++i) {
        tmp1 = cal(a[2], a[3], i);
        if (tmp1 == INF)
            continue;
        for (j=0; j<4; ++j) {
            tmp2 = cal(a[1], tmp1, j);
            if (tmp2 != INF) {
                for (k=0; k<4; ++k) {
                    ans = cal(a[0], tmp2, k);
                    if (ans != INF)
                        S.insert(ans);
                }
            }
        }
    }
}

int main() {
    int t = 0, n;
    int i, j, k;
    int ans;
    
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif
    
    while (scanf("%d%d%d%d",&a[0],&a[1],&a[2],&a[3])!=EOF && (a[0]+a[1]+a[2]+a[3])) {
        S.clear();
        sort(a, a+4);
        do {
            f();
        } while (next_permutation(a, a+4));
        n =0;
        for (iter=S.begin(); iter!=S.end(); ++iter)
            buf[n++] = *iter;
        ans = k = 0;
        for (i=1; i<n; ++i) {
            if (buf[i]==buf[i-1]+1)
                ++k;
            else
                k = 0;
            if (ans <= k) {
                ans = k;
                j = buf[i];
            }
        }
        printf("Case %d: %d to %d
", ++t, j-ans, j);
    }
    
    return 0;
}