Codeforces 623B Array GCD

Array GCD

最后的序列里肯定有a[1], a[1]-1, a[1]+1, a[n], a[n]-1, a[n]+1中的一个，枚举质因子， dp去check

#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 + ;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + ;
const double eps = 1e-;
 
LL n, a, b, tot, ans = INF;
LL c[N], fac[], dp[N][];
 
void solve(int x) {
    for(int i = ; i * i < x; i++) {
        if(x % i) continue;
        fac[tot++] = i;
        while(x % i == ) x /= i;
    }
    if(x > ) fac[tot++] = x;
    sort(fac, fac + tot);
    tot = unique(fac, fac + tot) - fac;
}
 
void calc(int fac) {
    memset(dp, INF, sizeof(dp));
    dp[][] = ;
    for(int i = , r1, r2, r3; i < n; i++) {
        r1 = (c[i + ] - ) % fac;
        r2 = r1 + ; if(r2 >= fac) r2 -= fac;
        r3 = r2 + ; if(r3 >= fac) r3 -= fac;
        if(dp[i][] < INF) {
            dp[i + ][] = min(dp[i + ][], dp[i][] + a);
            if(!r2) dp[i + ][] = min(dp[i + ][], dp[i][]);
            else if(!r1 || !r3) dp[i + ][] = min(dp[i + ][], dp[i][] + b);
        }
        if(dp[i][] < INF) {
            dp[i + ][] = min(dp[i + ][], dp[i][] + a);
            if(!r2) dp[i + ][] = min(dp[i + ][], dp[i][]);
            else if(!r1 || !r3) dp[i + ][] = min(dp[i + ][], dp[i][] + b);
        }
        if(dp[i][] < INF) {
            if(!r2) dp[i + ][] = min(dp[i + ][], dp[i][]);
            else if(!r1 || !r3) dp[i + ][] = min(dp[i + ][], dp[i][] + b);
        }
    }
    for(int i = ; i < ; i++)
        ans = min(ans, dp[n][i]);
}
 
int main() {
    scanf("%lld%lld%lld", &n, &a, &b);
    for(int i = ; i <= n; i++) scanf("%lld", &c[i]);
    for(int i = -; i <= ; i++) solve(c[] + i);
    for(int i = -; i <= ; i++) solve(c[n] + i);
    for(int i = ; i < tot; i++) calc(fac[i]);
    printf("%lld\n", ans);
    return ;
}
 
/*
*/