[pull] master from parallel101:master

15/06/a.cpp

@@ -0,0 +1,14 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "helloworld"s;
+    cout << "第0个字符:  " << s[0] << endl;
+    cout << "第3个字符:  " << s[3] << endl;
+    cout << "第16个字符: " << s[16] << endl;
+    cout << "第0个字符:  " << s.at(0) << endl;
+    cout << "第3个字符:  " << s.at(3) << endl;
+    cout << "第16个字符: " << s.at(16) << endl;
+}

15/06/a2.cpp

@@ -0,0 +1,11 @@
+#include <string>
+#include <string_view>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "hello";
+    cout << s.size() << endl;
+    cout << s.length() << endl;
+}

15/06/f.cpp

@@ -0,0 +1,20 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+size_t count(string const &str, string const &sub) {
+    size_t n = 0, pos = 0;
+    while (true) {
+        pos = str.find(sub, pos);
+        if (pos == str.npos)
+            break;
+        ++n;
+        pos += sub.size();
+    }
+    return n;
+}
+
+int main() {
+    cout << count("helloworld,bellreally"s, "ll"s) << endl;
+}

15/06/f2.cpp

@@ -0,0 +1,10 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "helloworld"s;
+    int n = s.find_first_of("onl");
+    cout << n << endl;
+}

15/06/f3.cpp

@@ -0,0 +1,28 @@
+#include <string>
+#include <vector>
+#include <iostream>
+
+using namespace std;
+
+vector<string> split(string s) {
+    vector<string> ret;
+    size_t pos = 0;
+    while (true) {
+        size_t newpos = s.find_first_of(" \t\v\f\n\r", pos);
+        if (newpos == s.npos) {
+            ret.push_back(s.substr(pos, newpos));
+            break;
+        }
+        ret.push_back(s.substr(pos, newpos - pos));
+        pos = newpos + 1;
+    }
+    return ret;
+}
+
+int main() {
+    string s = "hello world pyb teacher good job"s;
+    vector<string> v = split(s);
+    for (auto const &vi: v) {
+        cout << vi << endl;
+    }
+}

15/06/f4.cpp

@@ -0,0 +1,11 @@
+#include <string>
+#include <vector>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "hello world, pyb teacher? good job!"s;
+    int n = s.find_first_not_of(" abcdefghijklmnopqrstuvwxyz");
+    cout << n << endl;
+}

15/06/g.cpp

@@ -0,0 +1,10 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "make pyb happy"s;
+    s.replace(5, 3, "zhxx");    // 变成 make zhxx happy
+    cout << s << endl;
+}

15/06/h.cpp

@@ -0,0 +1,21 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+void replace_all(string &s, string const &from, string const &to) {
+    size_t pos = 0;
+    while (true) {
+        pos = s.find(from, pos);
+        if (pos == s.npos)
+            break;
+        s.replace(pos, from.size(), to);
+        pos += to.size();
+    }
+}
+
+int main() {
+    string s = "make pyb happy, as pyb said, cihou pyb"s;
+    replace_all(s, "pyb", "zhxx");
+    cout << s << endl;
+}

15/06/i.cpp

@@ -0,0 +1,24 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s;
+
+    s = "hello, "s;
+    s.append("world"s);    // "hello, world"
+    cout << s << endl;
+
+    s = "hello, "s;
+    s.append("world");     // "hello, world"
+    cout << s << endl;
+
+    s = "hello, "s;
+    s.append("world"s, 3); // "hello, ld"
+    cout << s << endl;
+
+    s = "hello, "s;
+    s.append("world", 3);  // "hello, wor"
+    cout << s << endl;
+}

15/06/j.cpp

@@ -0,0 +1,10 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    auto s = "HELLO"s;
+    s.insert(2, "world");
+    cout << s << endl;
+}

15/06/k.cpp

@@ -0,0 +1,10 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    auto s = "HELLO"s;
+    s = s.substr(0, 2) + "world"s + s.substr(2);
+    cout << s << endl;
+}

15/06/l.cpp

@@ -0,0 +1,15 @@
+#include <string>
+#include <string_view>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    auto s = "HELLO"s;
+    string_view sv = s;
+    string news;
+    news += sv.substr(0, 2);
+    news += "world"sv;
+    news += sv.substr(2);
+    cout << news << endl;
+}

15/07/c.cpp

@@ -0,0 +1,14 @@
+#include <string>
+#include <string_view>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s1 = "hello";
+    string_view sv1 = s1;
+    s1[0] = 'M';
+    cout << sv1 << endl;  // 不会失效
+    s1 = "helloworld";
+    cout << sv1 << endl;  // 失效!
+}

15/07/d.cpp

@@ -0,0 +1,12 @@
+#include <string>
+#include <string_view>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "hello";
+    string_view sv = s;
+    sv = sv.substr(1, 3);
+    cout << sv << endl;
+}

15/08/a.cpp

@@ -0,0 +1,28 @@
+#include <string>
+#include <vector>
+#include <string_view>
+#include <iostream>
+
+using namespace std;
+
+struct Empty {
+};
+
+struct NonEmpty {
+    char c;
+};
+
+struct DerivedEmpty : Empty {
+    int i;
+};
+
+struct DerivedNonEmpty : NonEmpty {
+    int i;
+};
+
+int main() {
+    cout << sizeof(Empty) << endl;            // 1 = 1(empty)
+    cout << sizeof(NonEmpty) << endl;         // 1 = 1(char c)
+    cout << sizeof(DerivedEmpty) << endl;     // 4 = 0(empty) + 4(int i)
+    cout << sizeof(DerivedNonEmpty) << endl;  // 8 = 1(char c) + 3(padding) + 4(int i)
+}

15/09/a.cpp

@@ -0,0 +1,55 @@
+#include <string>
+#include <iostream>
+#include <iomanip>
+#include <cstring>
+
+using namespace std;
+
+int main() {
+    cout << "\x7a\u00df\u6c34\U0001f34c" << endl;
+    {
+        cout << "char: ";
+        string s = "\x7a\u00df\u6c34\U0001f34c";
+        for (size_t i = 0; i < s.size(); i++) {
+            cout << setw(2) << setfill('0') << hex;
+            cout << hex << (uint32_t)(uint8_t)s[i] << ' ';
+        }
+        cout << endl;
+    }
+    {
+        cout << "wchar_t: ";
+        wstring s = L"\x7a\u00df\u6c34\U0001f34c";
+        for (size_t i = 0; i < s.size(); i++) {
+            cout << setw(sizeof(wchar_t) * 2) << setfill('0') << hex;
+            cout << (uint32_t)s[i] << ' ';
+        }
+        cout << endl;
+    }
+    //{
+        //cout << "char8_t: ";
+        //u8string s = u8"\x7a\u00df\u6c34\U0001f34c";
+        //for (size_t i = 0; i < s.size(); i++) {
+            //cout << setw(2) << setfill('0') << hex;
+            //cout << (uint16_t)s[i] << ' ';
+        //}
+        //cout << endl;
+    //}
+    {
+        cout << "char16_t: ";
+        u16string s = u"\x7a\u00df\u6c34\U0001f34c";
+        for (size_t i = 0; i < s.size(); i++) {
+            cout << setw(4) << setfill('0') << hex;
+            cout << (uint16_t)s[i] << ' ';
+        }
+        cout << endl;
+    }
+    {
+        cout << "char32_t: ";
+        u32string s = U"\x7a\u00df\u6c34\U0001f34c";
+        for (size_t i = 0; i < s.size(); i++) {
+            cout << setw(8) << setfill('0') << hex;
+            cout << (uint32_t)s[i] << ' ';
+        }
+        cout << endl;
+    }
+}

15/09/b.cpp

@@ -0,0 +1,71 @@
+#include <string>
+#include <string_view>
+#include <stdexcept>
+#include <iostream>
+#include <iomanip>
+#include <locale>
+
+using namespace std;
+
+template <class Internal = wchar_t>
+string convcodec(string_view src, locale const &srcLoc, locale const &dstLoc) {
+    auto strCodecvtError = [] (codecvt_base::result res) -> string {
+        if (res == codecvt_base::result::noconv)
+            return "noconv";
+        if (res == codecvt_base::result::error)
+            return "error";
+        if (res == codecvt_base::result::partial)
+            return "partial";
+        return "ok";
+    };
+
+    string dst;
+    basic_string<Internal> tmp;
+    mbstate_t mbstate = {};
+
+    auto &srcFacet = use_facet<codecvt<Internal, char, mbstate_t>>(srcLoc);
+    tmp.resize(src.size());
+
+    const char *src_begin = src.data();
+    const char *src_end = src.data() + src.size();
+    const char *src_next;
+    Internal *tmp_begin = tmp.data();
+    Internal *tmp_end = tmp.data() + tmp.size();
+    Internal *tmp_next;
+    auto resIn = srcFacet.in(mbstate, src_begin, src_end, src_next, tmp_begin, tmp_end, tmp_next);
+    if (resIn != codecvt_base::result::ok)
+        throw runtime_error("cannot decode input sequence: " + strCodecvtError(resIn));
+    size_t tmp_size = tmp_next - tmp_begin;
+    tmp_end = tmp_next;
+
+    auto &dstFacet = use_facet<codecvt<Internal, char, mbstate_t>>(dstLoc);
+    dst.resize(tmp_size * dstFacet.max_length());
+
+    char *dst_begin = dst.data();
+    char *dst_end = dst.data() + dst.size();
+    char *dst_next;
+    const Internal *tmp_next_next;
+    auto resOut = dstFacet.out(mbstate, tmp_begin, tmp_end, tmp_next_next, dst_begin, dst_end, dst_next);
+    if (resOut != codecvt_base::result::ok)
+        throw runtime_error("cannot encode output sequence: " + strCodecvtError(resOut));
+    size_t dst_size = dst_next - dst_begin;
+
+    dst.resize(dst_size);
+    return dst;
+}
+
+void showstr(string_view s) {
+    for (char c: s) {
+        cout << hex << setfill('0') << setw(2);
+        cout << (uint32_t)(uint8_t)c << ' ';
+    }
+    cout << s << endl;
+}
+
+int main() {
+    string s = "你好";
+    //string s = "你好\U0001f34c";  // error: cannot encode U+1F34C
+    showstr(s);
+    s = convcodec(s, locale("en_US.UTF-8"), locale("zh_CN.GBK"));
+    showstr(s);
+}