[itint5]两有序数组的交和并

这一题也简单，唯一有意思的地方是提炼了一个函数用来做数组索引去重前进。

int forward(vector<int> &arr, int i) {
    while (i+1 < arr.size() && arr[i] == arr[i+1]) i++;
    i++;
    return i;
}

vector<int> arrayUnion(vector<int> &a, vector<int> &b) {
    vector<int> ans;
    int i = 0;
    int j = 0;
    while (i < a.size() && j < b.size()) {
        if (a[i] == b[j]) {
            ans.push_back(a[i]);
            i = forward(a, i);
            j = forward(b, j);
        } else if (a[i] < b[j]) {
            ans.push_back(a[i]);
            i = forward(a, i);
        } else {
            ans.push_back(b[j]);
            j = forward(b, j);
        }
    }
    while (i < a.size()) {
        ans.push_back(a[i]);
        i = forward(a, i);
    }
    while (j < b.size()) {
        ans.push_back(b[j]);
        j = forward(b, j);
    }
    return ans;
}

vector<int> arrayIntersect(vector<int> &a, vector<int> &b) {
    vector<int> ans;
    int i = 0;
    int j = 0;
    while (i < a.size() && j < b.size()) {
        if (a[i] == b[j]) {
            ans.push_back(a[i]);
            i = forward(a, i);
            j = forward(b, j);
        } else if (a[i] < b[j]) {
            i = forward(a, i);
        } else {
            j = forward(b, j);
        }
    }
    return ans;
}