Blog entries - Codeforces

Problem.

I solved the problem with three pointers. But when I sort the vectors first and the resize, I get an AC. If I sort them after making them unique, I get a WA.

AC Code

long triplets(vector<int> a, vector<int> b, vector<int> c) {
    sort(all(a));
    sort(all(b));
    sort(all(c));
    a.erase(unique(all(a)), a.end());
    b.erase(unique(all(b)), b.end());
    c.erase(unique(all(c)), c.end());
    int n = a.size(), m = b.size(), l = c.size();
    int i = 0, j = 0, k = 0;
    long ans = 0;
    for(int j = 0; j < m; j++) {
        while(i < n and a[i] <= b[j]) i++;
        while(k < l and c[k] <= b[j]) k++;
        ans += 1LL*i*k;
    }
    return ans;
}

WA Code

long triplets(vector<int> a, vector<int> b, vector<int> c) {
    a.erase(unique(all(a)), a.end());
    b.erase(unique(all(b)), b.end());
    c.erase(unique(all(c)), c.end());
    sort(all(a));
    sort(all(b));
    sort(all(c));
    int n = a.size(), m = b.size(), l = c.size();
    int i = 0, j = 0, k = 0;
    long ans = 0;
    for(int j = 0; j < m; j++) {
        while(i < n and a[i] <= b[j]) i++;
        while(k < l and c[k] <= b[j]) k++;
        ans += 1LL*i*k;
    }
    return ans;
}

Full text and comments »

#	User	Rating
1	Benq	3792
2	VivaciousAubergine	3647
3	Kevin114514	3603
4	jiangly	3583
5	strapple	3515
6	tourist	3470
7	dXqwq	3436
8	Radewoosh	3415
9	Otomachi_Una	3413
10	Um_nik	3376

#	User	Contrib.
1	Qingyu	158
2	adamant	152
3	Proof_by_QED	146
3	Um_nik	146
5	Dominater069	144
6	errorgorn	141
7	cry	139
8	YuukiS	135
9	chromate00	134
9	TheScrasse	134

aneee's blog