2019牛客多校第三场J-LRU management(map+双向链表)

LRU management

题目传送门

解题思路

用map索引对应地址，用双向链表维护序列。

代码如下

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;

inline int read(){
    int res = 0, w = 0; char ch = 0;
    while(!isdigit(ch)){
        w |= ch == '-', ch = getchar();
    }
    while(isdigit(ch)){
        res = (res << 3) + (res << 1) + (ch ^ 48);
        ch = getchar();
    }
    return w ? -res : res;
}

const int N = 500005;

int l[N], r[N];
int data[N], cnt, tail, sum, front;
ll u[N];
map<ll, int> mp;

int main()
{
    int t;
    t = read();
    while(t --){
        int q, m;
        scanf("%d%d%*c", &q, &m);
        front = sum = tail = cnt = 0;
        for(int i = 0; i <= q + 1; i ++)
            u[i] = l[i] = r[i] = data[i] = 0;
        for(int i = 1; i <= q; i ++){
            int opt;
            scanf("%d%*c", &opt);
            ll s = 1;
            char ch;
            while((ch = getchar()) != ' ')
                s = s * 10 + ch - '0';
            int v;
            scanf("%d", &v);
            if(opt == 0){
                if(mp.find(s) == mp.end()){
                    data[++cnt] = v;
                    u[cnt] = s;
                    mp[s] = cnt;
                    r[tail] = cnt;
                    l[cnt] = tail;
                    r[cnt] = 0;
                    tail = cnt;
                    printf("%d\n", v);
                    if(sum == 0)
                        front = cnt;
                    ++ sum;
                }
                else {
                    int k = mp[s];
                    printf("%d\n", data[k]);
                    if(sum > 1){
                        if(k == front)
                            front = r[k];
                        if(k != tail){
                            r[l[k]] = r[k];
                            l[r[k]] = l[k];
                            r[tail] = k;
                            l[k] = tail;
                            r[k] = 0;
                            tail = k;
                        }
                    }
                }
                if(sum > m){
                    -- sum;
                    mp.erase(u[front]);
                    front = r[front];
                    l[front] = 0;
                }
            }
            else {
                if(mp.find(s) == mp.end()){
                    puts("Invalid");
                    continue;
                }
                int k = mp[s];
                if(v == -1){
                    if(l[k])
                        printf("%d\n", data[l[k]]);
                    else
                        puts("Invalid");
                }
                else if(v == 0){
                    printf("%d\n", data[k]);
                }
                else {
                    if(r[k])
                        printf("%d\n", data[r[k]]);
                    else
                        puts("Invalid");
                }
            }
        }
        mp.clear();
    }
    return 0;
}