C++ 代码

# include <iostream>
# include <string>

using namespace std;

const int N = 1e6 + 10;
const int DEFAULT = -100;

int l[N], r[N], head_idx, tail_idx, e[N], idx;

void init() {
    head_idx = 0;
    tail_idx = 1;
    idx = 2;
    r[head_idx] = tail_idx;
    l[tail_idx] = head_idx;
    r[tail_idx] = DEFAULT;
    l[head_idx] = DEFAULT;
}

void addNodeTokRight(int k, int value) {
    int k_idx = k + 1;
    if (k == 0) {
        k_idx = 0;
    }

    if (k_idx == 1) {
        cout << "cannot add to tail's right\n";
        exit(0);
    }
    e[idx] = value;
    l[idx] = k_idx;
    r[idx] = r[k_idx];
    l[r[k_idx]] = idx;
    r[k_idx] = idx;
    idx++;
}

void addNodeTokLeft(int k, int value) {
    int k_idx = k + 1;
    int kLeft_idx = l[k_idx];
    addNodeTokRight(kLeft_idx - 1, value);
}

//在链表的最左端插入数  -> 在 head的右端插入
void addNodeToLeft(int value) {
    addNodeTokRight(head_idx, value);
}

//在链表的最右端插入数 -> 在tail的左节点的右端插入
void addNodeToRight(int value) {
    int k_idx = l[tail_idx];
    if (k_idx == 0) {
        addNodeTokRight(0, value);
    }
    else {
        addNodeTokRight(k_idx - 1, value);
    }

}

//将第 k 个插入的数删除
void remove(int k) {
    if (k < 1) {
        cout << "k must be >= 1\n";
        exit(0);
    }
    int k_idx = k + 1;
    r[l[k_idx]] = r[k_idx];
    l[r[k_idx]] = l[k_idx];
}

void printList() {
    int index = head_idx;
    index = r[index];
    while (index != 1) {
        printf("%d ", e[index]);
        index = r[index];
    }
    printf("\n");
}

int main() {
    int M;
    cin >> M;
    string op;
    int k, x;
    init();
    for (int i = 0; i < M; i++) {
        cin >> op;
        if (op == "L") {
            cin >> x;
            addNodeToLeft(x);
        }
        else if (op == "R") {
            cin >> x;
            addNodeToRight(x);
        }
        else if (op == "D") {
            cin >> k;
            remove(k);
        }
        else if (op == "IL") {
            cin >> k;
            cin >> x;
            addNodeTokLeft(k, x);
        }
        else if (op == "IR") {
            cin >> k;
            cin >> x;
            addNodeTokRight(k, x);
        }
        else {
            cout << "Illegal command\n";
            return 0;
        }
        //printf("the %d op is : ", i);
        //printList();
    }
    printList();
    return 0;
}