BZOJ1562 – [NOI2009]变换序列

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#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;
const int MAX_N = 20000 + 1000;
int N;

struct tgno {
    int v;
    tgno* n;
} POOL[MAX_N], *Head[MAX_N]; int ppos = 0;

void addEdge(int u, int v) {
    POOL[ppos].v = v;
    POOL[ppos].n = Head[u];
    Head[u] = &POOL[ppos++];
}

int cnt;
int p[MAX_N], vis[MAX_N];

bool dfs(int a) {
    for(tgno* it=Head[a];it;it=it->n) {
        if(vis[it->v] != cnt) {
            vis[it->v] = cnt;
            if(!p[it->v] || dfs(p[it->v])) {
                p[it->v] = a;
                return true;
            }
        }
    }
    return false;
}

int main() {
    scanf("%d", &N);
    
    in
    t;
    for(int i=0;i<N;i++) {
        scanf("%d", &t);
        int x1 = (i - t + N) % N;
        int x2 = (i + t + N) % N;
        if(x1 > x2) swap(x1, x2);
        addEdge(i, x2); addEdge(i, x1);
    }
    
    cnt = 0;
    int ans[MAX_N];
    for(int i=N-1;i>=0;i--) {
        cnt++;
        if(!dfs(i)) { printf("No Answern"); return 0; }
    }
    
    for(int i=0;i<N;i++) {
        ans[p[i]] = i;
    }
    
    printf("%d", ans[0]);
    for(int i=1;i<N;i++) {
        printf(" %d", ans[i]);
    }
    printf("n");
    
    #ifdef LCYTEST
    system("pause");
    #endif
}