SOJ 1180. Pasting Strings

结合样例和下面图中的几种情况考虑即可解决。

代码如下：

#include <iostream>
#include <stack>
#include <string>
using namespace std;

int main() {
    int begin, end;
    while (cin >> begin >> end, begin != -1 && end != -1) {
        string text;
        cin.get(); getline(cin, text);
        stack<string> prepend, append;
        for (int cur = 0; cur < begin; ++cur) {
            if (text[cur] == '<') {
                if (text[cur + 1] == '/') {
                    prepend.pop(); append.pop();
                } else {
                    int tail = cur + 1;
                    while (text[tail] != '>') ++tail;
                    string tag = text.substr(cur, tail - cur + 1);
                    prepend.push(tag);
                    append.push(tag.insert(1, "/"));
                }
            }
        }
        for (int cur = begin; cur < end; ++cur) {
            if (text[cur] == '<') {
                if (text[cur + 1] == '/') {
                    append.pop();
                } else {
                    int tail = cur + 1;
                    while (text[tail] != '>') ++tail;
                    string tag = text.substr(cur, tail - cur + 1);
                    append.push(tag.insert(1, "/"));
                }
            }
        }
        string ans = text.substr(begin, end - begin);
        while (!prepend.empty()) {
            ans = prepend.top() + ans; prepend.pop();
        }
        while (!append.empty()) {
            ans += append.top(); append.pop();
        }
        cout << ans << endl;
    }
    return 0;
}