度度熊剪纸条

ps：改了这么久，对拍一下就找到错误了。贪心，首部出现的1，是不用去剪的，所以当作特殊元素考虑，因此当 k == 0的时候 或者 k没有用完的时候一定要考虑是否用到了首部那一节（cntSt)。而尾部只需要剪一次，中间的部分需要减两次，贪心的时候要分别讨论（有史以来写得最丑的代码！！！)

inline bool cmp(P a, P b) {
    return a.first > b.first;
}

int main()
{
    while (scanf("%d %d", &n, &k) != EOF) {

        scanf("%s", s);
        int cntSt = 0, cntEd = 0, st = 0, ed = n - 1;
        for (int i = 0; i < n; ++i) {
            if (s[i] != '1') {
                st = i;
                break;
            }
            else cntSt++;
        }
        for (int i = n - 1; ~i; --i) {
            if (s[i] != '1') {
                ed = i;
                break;
            }
            else cntEd++;
        }
        if (cntEd == n) {
            cout << n << endl;
            continue;
        }

        vector<int> ans;
        ans.clear();
        mem(use, 0);

        P p[N];

        int t = 0;
        for (int i = st; i <= ed; ++i) {
            if (s[i] == '1') t++;
            else {
                if (t) ans.pb(t);
                t = 0;
            }
        }
        if (t) ans.pb(t);

        if (k == 0) {
            cout << cntSt << endl;
            continue;
        }
        if (k == 1) {
            int res = cntEd + cntSt;
            for (int i = 0; i < ans.size(); ++i) upd(res, ans[i]);
            cout << res << endl;
            continue;
        }

        for (int i = 0; i < ans.size(); ++i) p[i].first = ans[i], p[i].second = 0;
        if (cntEd) p[ans.size()].first = cntEd, p[ans.size()].second = 1;
        sort(p, p + ans.size() + 1, cmp);


        int res = 0;
        for (int i = 0; i < ans.size() + 1; ++i) {
            if (!k) break;
            if (p[i].second == 1) {
                res += p[i].first;
                k--;
                use[cntEd] = 1;
                if (k == 0) res += cntSt;             }
            else {
                if (k > 2) {
                    res += p[i].first;
                    k -= 2;
                }
                else if (k == 2) {
                    if (use[cntEd]) res += p[i].first + cntSt;
                    else res += max(p[i].first + cntSt, p[i].first + cntEd);
                    k -= 2;
                }
                else if (k == 1) {
                    if (use[cntEd]) res += max(cntSt, p[i].first);
                    else res += max(cntSt + cntEd, p[i].first);
                    k--;
                }
            }
        }
        if (k) res += cntSt;
        cout << res << endl;
    }
    return 0;
}