Codeforces 1149 B - Three Religions

B - Three Religions

思路：dp

dp[i][j][k]：a的前i个和b的前j个和c的前k个能构成的最前面的位置

删字符时状态不用改变，加字符时只会改变1*250*250个状态

代码：

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize(4)
#include<bits/stdc++.h>
using namespace std;
#define y1 y11
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
//#define mp make_pair
#define pb push_back
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pli pair<LL, int>
#define pii pair<int, int>
#define piii pair<pii, int>
#define pdi pair<double, int>
#define pdd pair<double, double>
#define mem(a, b) memset(a, b, sizeof(a))
#define debug(x) cerr << #x << " = " << x << "\n";
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//head

const int N = 1e5 + 5;
char s[N];
int nxt[N][26], n, q, x;
char op[10], cc[10];
int dp[255][255][255];
string a, b, c;
int main() {
    scanf("%d %d", &n, &q);
    scanf("%s", s+1);
    for (int i = 0; i < 26; ++i) nxt[n+1][i] = n+1, nxt[n+2][i] = n+1;
    for (int i = n; i >= 1; --i) {
        for (int j = 0; j < 26; ++j) {
            if(j == s[i]-'a') nxt[i][j] = i;
            else nxt[i][j] = nxt[i+1][j];
        }
    }
    while(q--) {
        scanf("%s %d", op, &x);
        if(op[0] == '+') {
            scanf("%s", cc);
            if(x == 1){
                a.push_back(cc[0]);
                for (int i = 0; i <= b.size(); ++i) {
                    for (int j = 0; j <= c.size(); ++j) {
                        dp[a.size()][i][j] = n+1;
                        if(a.size() > 0) dp[a.size()][i][j] = min(dp[a.size()][i][j], nxt[dp[a.size()-1][i][j]+1][a.back()-'a']);
                        if(i > 0) dp[a.size()][i][j] = min(dp[a.size()][i][j], nxt[dp[a.size()][i-1][j]+1][b[i-1]-'a']);
                        if(j > 0) dp[a.size()][i][j] = min(dp[a.size()][i][j], nxt[dp[a.size()][i][j-1]+1][c[j-1]-'a']);
                    }
                }
            }
            else if(x == 2) {
                b.push_back(cc[0]);
                for (int i = 0; i <= a.size(); ++i) {
                    for (int j = 0; j <= c.size(); ++j) {
                        dp[i][b.size()][j] = n+1;
                        if(b.size() > 0) dp[i][b.size()][j] = min(dp[i][b.size()][j], nxt[dp[i][b.size()-1][j]+1][b.back()-'a']);
                        if(i > 0) dp[i][b.size()][j] = min(dp[i][b.size()][j], nxt[dp[i-1][b.size()][j]+1][a[i-1]-'a']);
                        if(j > 0) dp[i][b.size()][j] = min(dp[i][b.size()][j], nxt[dp[i][b.size()][j-1]+1][c[j-1]-'a']);
                    }
                }
            }
            else if(x == 3) {
                c.push_back(cc[0]);
                for (int i = 0; i <= a.size(); ++i) {
                    for (int j = 0; j <= b.size(); ++j) {
                        dp[i][j][c.size()] = n+1;
                        if(c.size() > 0) dp[i][j][c.size()] = min(dp[i][j][c.size()], nxt[dp[i][j][c.size()-1]+1][c.back()-'a']);
                        if(i > 0) dp[i][j][c.size()] = min(dp[i][j][c.size()], nxt[dp[i-1][j][c.size()]+1][a[i-1]-'a']);
                        if(j > 0) dp[i][j][c.size()] = min(dp[i][j][c.size()], nxt[dp[i][j-1][c.size()]+1][b[j-1]-'a']);
                    }
                }
            }
        }
        else {
            if(x == 1) a.pop_back();
            else if(x == 2) b.pop_back();
            else if(x == 3) c.pop_back();
        }
        if(dp[a.size()][b.size()][c.size()] > n) printf("NO\n");
        else printf("YES\n");
    }
    return 0;
}

 

来源：https://www.cnblogs.com/widsom/p/10808527.html