C++正则匹配字符串中匹配项位置获取问题求助

我在实现获取字符串中正则匹配项位置的算法时遇到了问题，代码如下：

std::vector<int> mval;

int closed_val = 0;
int open_val = 0;
std::string da_line = "} } }";
std::smatch m;
std::regex_search(da_line, m, std::regex("([\}]+)"));
for (auto mv : m) std::cout << mv << std::endl;
std::cout << m.size() << std::endl;
closed_val = da_line.find(m[0]);
mval.push_back(closed_val);
try {
    if (m.size() >= 1) {
        std::string db_line;
        for (int j = 1; j < m.size(); j++) {
            std::cout << da_line << std::endl;
            db_line = da_line.substr(da_line.find(m[j]) + 1, da_line.size() - 1);
            std::cout << db_line << std::endl;
            int f = db_line.find(m[j]);
            if (f == -1 || f > db_line.size() - 1)
                continue;
                std::cout << f << std::endl;
            open_val = closed_val + f + 1;
            for (auto mv : m) std::cout << mv << std::endl;
            std::cout << db_line.find(m[j + 1]) << std::endl;
            mval.push_back(open_val);
            closed_val = open_val;
            da_line = db_line;
        }
    }
}
catch (std::exception& error) {
    std::cerr << "error : " << error.what() << std::endl;
}

for (auto mv : mval) std::cout << mv << ":";
std::cout << std::endl;

当前输出：

}
}
2
} } }
 } }
1
}
}
0
0:2:

存在两个问题：

• 字符串中有3个}，但正则返回了2个匹配；
• 预期结果为0:2:4，但实际输出为0:2。

内容的提问来源于stack exchange，提问作者SagunKho