【模拟】V字形打印字符

void vprint(string s, int level) {
    int len = s.size();
    int l_gap_num = 2 * (level - 1) - 1;
    int r_gap_num = -1;
    for (int l = 0; l < level; l++) {
        // 第几行先打印即可空格
        cout << string(l, ' ');
        
        if (l == 0 || l == level - 1) {
            // 首行和尾行间隔是一样的
            int gap = (l == 0) ? l_gap_num  : r_gap_num;
            for (int i = l; i < len; i += gap + 1) {
                cout << s[i];
                cout << string(gap, ' ');
            }
            cout << endl;
        }else{
            // 中间行两种间隔l_gap_num、r_gap_num交替打印
            int gap = l_gap_num;
            bool flag = true;
            int idx = l;
            while (idx < len) {
                cout << s[idx];
                cout << string(gap, ' ');
                idx += (gap + 1);
                gap = flag ? r_gap_num : l_gap_num;
                flag = !flag;
            }
            cout << endl;
        }
          
        l_gap_num -= 2;
        r_gap_num += 2;
    }
}