Codeforces 1028E Restore Array 构造

我发现我构造题真的不会写， 想了好久才想出来。。

我们先把n = 2， 所有数字相等， 所有数字等于0的都特判掉。

找到一个b[ i ] > b[ i - 1 ]的位置把它移到最后一个位置， 并且使其a[ i ] = b[ i ]然后从后往前构造。

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ull unsigned long long

using namespace std;

const int N = 1e6 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-8;
const double PI = acos(-1);

int n, who = -1, id[N];
LL a[N], b[N];
bool flag;
int main() {
    scanf("%d", &n);
    for(int i = 0; i < n; i++) {
        scanf("%lld", &b[i]);
        flag |= b[i];
    }
    for(int i = 0; i < n; i++) {
        if(b[(i-1+n)%n] < b[i]) who = i;
    }
    if(!flag) {
        puts("YES");
        for(int i = 0; i < n; i++) printf("1 ");
        puts("");
    } else if(n == 2) {
        if(a[0] == a[1]) puts("NO");
        else {
            puts("YES");
            if(a[0] > a[1]) printf("%lld %lld\n", a[0], a[0] + a[1]);
            else printf("%lld %lld\n", a[0] + a[1], a[1]);
        }
    } else {
        if(who == -1) return puts("NO"), 0;
        int now = 0, cur = (who + 1) % n;
        for(int i = 1; i <= n; i++) {
            id[now++] = cur;
            cur = (cur + 1) % n;
        }
        a[id[n - 1]] = b[id[n - 1]];
        for(int i = n - 2; i >= 0; i--) {
            LL low = b[id[(i - 1 + n) % n]] + 1;
            LL mo = a[id[i + 1]];
            a[id[i]] = low + (((b[id[i]] % mo) - (low % mo)) % mo + mo) % mo;
        }
        puts("YES");
        for(int i = 0; i < n; i++) printf("%lld ", a[i]);
        puts("");
    }
    return 0;
}

/*
*/