A. Two Substrings;int main() {string str;while (cin >> str) {vector<int> ab;vector<int> ba;for (int i = 0; i < str.length() – 1; ++i) {if (str[i] == ‘A’ && str[i + 1] == ‘B’) {ab.push_back(i);} else if (str[i] == ‘B’ && str[i + 1] == ‘A’) {ba.push_back(i);}}bool flag = false;for (int i = 0; i < ab.size(); ++i) {for (int j = 0; j < ba.size(); ++j) {if (abs(ab[i] – ba[j]) > 1) {flag = true;break;}}if (flag) {break;}}cout << (flag ? “YES” : “NO”) << endl;}return 0;}B. Preparing Olympiad题意：个问题，每个问题有一个难度值，，要选出来一些。问满足以下条件的方案数： 题解：数据很小地得到。参考代码：;const int MAX = 16;int sum[MAX];int c[MAX];int n, l, r, x;bool check(int state) {int sum = 0, mind = 0xfffffff, maxd = -1;for (int i = 0; i < n; ++i) {if (state & 1) {sum += c[i];if (c[i] > maxd) {maxd = c[i];}if (c[i] < mind) {mind = c[i];}}state >>= 1;}if (sum < l || sum > r || (maxd – mind) < x) {return false;}return true;}int main() {while (~scanf(” %d %d %d %d”, &n, &l, &r, &x)) {for (int i = 0; i < n; ++i) {scanf(” %d”, c + i);}sort(c, c + n);memset(sum, 0, sizeof(sum));sum[0] = c[0];for (int i = 1; i < n; ++i) {sum[i] = sum[i – 1] + c[i];}int ans = 0;for (int i = 0; i < (1 << n); ++i) {if (check(i)) {ans++;}}printf(“%d\n”, ans);}return 0;}C. Divisibility by Eight;pair<bool, string> judge1(string x) {for (int i = x.length() – 1; i >= 0; –i) {if (x[i] == ‘0’) {return make_pair(true, “0”);}}return make_pair(false, “joke”);}bool judge2(int x) {if (x == 0) {return false;}while (x) {if (x % 10 == 0) {return false;}x /= 10;}return true;}string toString(int x) {string res = “”;if (x == 0) {res = “0”;}while (x) {res = (char)(x % 10 + ‘0’) + res;x /= 10;}return res;}void init(vector<string>& x) {for (int i = 1; i < 1000; ++i) {if (i % 8 == 0 && judge2(i)) {//printf(“push %d\n”, i);x.push_back(toString(i));}}}pair<bool, string> judge3(string x, string sub) {//cout << “Judge3(” << x << “, ” << sub << “)” << endl;int i = 0, j = 0;while (i < x.size() && j < sub.size()) {if (x[i] == sub[j]) {++i;++j;} else {++i;}}if (j == sub.size()) {return make_pair(true, sub);} else {return make_pair(false, “fuck”);}}int main() {//cout << toString(344) << endl;vector<string> box;init(box);string num;while (cin >> num) {pair<bool, string> ans = judge1(num);if (ans.first) {cout << “YES\n0” << endl;} else {bool flag = false;for (int i = 0; i < box.size(); ++i) {ans = judge3(num, box[i]);if (ans.first) {cout << “YES\n” << ans.second << endl;flag = true;break;}}if (!flag) {cout << “NO” << endl;}}}return 0;}D和E留着下次补…
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