12657 - Boxes in a Line （UVA）

题目链接如下：

Online Judge

代码如下：

#include 
#include 
// #define debug
const int maxx = 100010;
 
int n, m, kase, op, a, b;
int prev[maxx], next[maxx];
 
int main(){
    #ifdef debug
    freopen("0.txt", "r", stdin);
    freopen("1.txt", "w", stdout);
    #endif
    kase = 0;
    while (scanf("%d %d", &n, &m) == 2){
        bool flag = true;
        for (int i = 0; i <= n + 1; ++i){
            next[i] = i + 1;
            prev[i] = i - 1;
        }
        while (m--){
            scanf("%d", &op);
            if (op == 4){
                flag = !flag;
            } else {
                scanf("%d %d", &a, &b);
                if ((op == 1 && ((flag && next[a] == b) || (!flag && prev[a] == b))) || (op == 2 && ((flag && prev[a] == b) || (!flag && next[a] == b)))){
                    continue;
                }
                if ((op == 1 && flag) || (op == 2 && !flag)){
                    prev[next[a]] = prev[a];
                    next[prev[a]] = next[a];
                    next[prev[b]] = a;
                    prev[a] = prev[b];
                    next[a] = b;
                    prev[b] = a;
                } else if ((op == 1 && !flag) || (op == 2 && flag)){
                    prev[next[a]] = prev[a];
                    next[prev[a]] = next[a];
                    prev[next[b]] = a;
                    next[a] = next[b];
                    next[b] = a;
                    prev[a] = b;
                } else if (op == 3){
                    if (next[a] == b){
                        next[prev[a]] = b;
                        prev[b] = prev[a];
                        next[a] = next[b];
                        prev[next[b]] = a;
                        prev[a] = b;
                        next[b] = a;
                    } else if (prev[a] == b){
                        next[prev[b]] = a;
                        prev[a] = prev[b];
                        prev[next[a]] = b;
                        next[b] = next[a];
                        prev[b] = a;
                        next[a] = b;
                    } else{
                        prev[next[a]] = b;
                        next[prev[a]] = b;
                        prev[next[b]] = a;
                        next[prev[b]] = a;
                        std::swap(next[a], next[b]);
                        std::swap(prev[a], prev[b]);
                    }
                }
            }
        }
        long long ans = 0;
        if (flag){
            for (int i = next[0]; i > 0 && i <= n; i = next[i]){
                ans += i;
                i = next[i];
            }
        } else {
            for (int i = prev[n + 1]; i > 0 && i <= n; i = prev[i]){
                ans += i;
                i = prev[i];
            }
        }
        printf("Case %d: %lld\n", ++kase, ans);
    }
    #ifdef debug
    fclose(stdin);
    fclose(stdout);
    #endif
    return 0;
}