Codeforces 1137B（kmp next数组构造）

Posted 2021-02-16 alphawa

为了物尽其用，Next求出最多有哪部分能重复使用，然后重复使用就行了……

const int maxn = 5e5 + 5;
char s[maxn], t[maxn];
int cnts0, cnts1, cntt0, cntt1;
int Next[maxn];

int main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cin >> (s + 1) >> (t + 1);
    int lens = strlen(s + 1), lent = strlen(t + 1);

    for (int i = 1; i <= lens; i++) {
        if (s[i] == '1')    cnts1++;
        else    cnts0++;
    }

    Next[1] = 0;
    for (int i = 2, j = 0; i <= lent; i++) {
        while (j > 0 && t[i] != t[j + 1])   j = Next[j];
        if (t[i] == t[j + 1])   j++;
        Next[i] = j;
    }

    for (int i = Next[lent] + 1; i <= lent; i++) {
        if (t[i] == '1')    cntt1++;
        else    cntt0++;
    }

    for (int i = 1; i <= lent; i++) {
        if (t[i] == '1' && cnts1)   cout << 1, cnts1--;
        else if (t[i] == '0' && cnts0)  cout << 0, cnts0--;
    }
    int k = min(cntt0 ? cnts0 / cntt0 : inf, cntt1 ? cnts1 / cntt1 : inf);
    while (k--) {
        for (int i = Next[lent] + 1; i <= lent; i++) {
            if (t[i] == '1')    cout << 1, cnts1--;
            else    cout << 0, cnts0--;
        }
    }
    while (cnts1--) cout << 1;
    while (cnts0--) cout << 0;
    
    return 0;
}