[pull] master from parallel101:master

15/04/a.cpp

@@ -0,0 +1,10 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    int n = 42;
+    auto s = to_string(n) + " yuan"s;
+    cout << s << endl;
+}

15/04/b.cpp

@@ -0,0 +1,10 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    auto s = "42 yuan"s;
+    int n = stoi(s);
+    cout << n << endl;
+}

15/04/c.cpp

@@ -0,0 +1,14 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "42yuan"s;
+    size_t pos;
+    int n = stoi(s, &pos);
+    cout << "原始字符串: " << s << endl;
+    cout << "数字部分从第" << pos << "个字符结束" << endl;
+    cout << "数字是" << n << endl;
+    cout << "剩余的部分是" << s.substr(pos) << endl;
+}

15/04/d.cpp

@@ -0,0 +1,12 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "4399cc"s;
+    cout << "原始字符串" << s << endl;
+    cout << "作为十六进制" << stoi(s, nullptr, 16) << endl;  // 0x4399cc
+    cout << "作为十进制" << stoi(s, nullptr, 10) << endl;    // 4399
+    cout << "作为八进制" << stoi(s, nullptr, 8) << endl;     // 043
+}

15/04/e.cpp

@@ -0,0 +1,11 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "happy 10th birthday"s;
+    cout << "字符串: " << s << endl;
+    int n = stoi(s);
+    cout << "数字是: " << n << endl;
+}

15/04/f.cpp

@@ -0,0 +1,12 @@
+#include <string>
+#include <iostream>
+#include <functional>
+
+using namespace std;
+
+int main() {
+    string s = "+03.14e-03"s;
+    cout << "字符串: " << s << endl;
+    float f = stof(s);
+    cout << "浮点数: " << f << endl;
+}

15/05/a.cpp

@@ -0,0 +1,9 @@
+#include <string>
+#include <iostream>
+#include <iomanip>
+
+using namespace std;
+
+int main() {
+    cout << "十六进制：" << hex << 42 << endl;
+}

15/05/b.cpp

@@ -0,0 +1,13 @@
+#include <string>
+#include <iostream>
+#include <sstream>
+#include <iomanip>
+
+using namespace std;
+
+int main() {
+    stringstream ss;
+    ss << "十六进制：" << hex << 42;
+    string s = ss.str();
+    cout << s << endl;
+}

15/05/c.cpp

@@ -0,0 +1,17 @@
+#include <string>
+#include <iostream>
+#include <sstream>
+#include <iomanip>
+
+using namespace std;
+
+int main() {
+    string s = "42yuan"s;
+    stringstream ss(s);
+    int num;
+    ss >> num;
+    string unit;
+    ss >> unit;
+    cout << "数字：" << num << endl;
+    cout << "单位：" << unit << endl;
+}

15/06/b.cpp

@@ -0,0 +1,13 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "helloworld"s;
+    cout << "从第2个字符开始长为5的子字符串:    " << s.substr(2, 4) << endl;
+    cout << "从第2个字符开始长为99的子字符串:   " << s.substr(2, 99) << endl;
+    cout << "从第2个字符开始直到末尾的子字符串: " << s.substr(2) << endl;
+    cout << "从头开始长为5的子字符串:           " << s.substr(0, 4) << endl;
+    cout << "从第100个字符开始长为5的子字符串:  " << s.substr(100, 5) << endl;
+}

15/06/c.cpp

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+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "helloworld"s;
+    cout << "寻找h的结果：" << s.find('h') << endl;
+    cout << "寻找e的结果：" << s.find('e') << endl;
+    cout << "寻找l的结果：" << s.find('l') << endl;
+    cout << "寻找o的结果：" << s.find('o') << endl;
+    cout << "寻找H的结果：" << s.find('H') << endl;
+    cout << "(size_t) -1：" << (size_t)-1 << endl;
+}

15/06/d.cpp

@@ -0,0 +1,11 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "helloworld"s;
+    cout << boolalpha;
+    cout << "h: " << (s.find('h') != string::npos) << endl;
+    cout << "z: " << (s.find('z') != string::npos) << endl;
+}

15/06/e.cpp

@@ -0,0 +1,12 @@
+#include <string>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s = "helloworld"s;
+    cout << boolalpha;
+    cout << "lo: " << s.find("lo") << endl;
+    cout << "wo: " << s.find("wo") << endl;
+    cout << "ma: " << s.find("ma") << endl;
+}

15/07/a.cpp

@@ -0,0 +1,9 @@
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+int main() {
+    cout << string("hello\0cpp") << endl;
+    cout << string("hello\0cpp", 9) << endl;
+}

15/07/b.cpp

@@ -0,0 +1,22 @@
+#include <string>
+#include <string_view>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    string s1 = "hello";
+    string s2 = s1;         // 深拷贝
+    string_view sv1 = s1;   // 弱引用
+    string_view sv2 = sv1;  // 浅拷贝
+    cout << "s1=" << s1 << endl;
+    cout << "s2=" << s2 << endl;
+    cout << "sv1=" << sv1 << endl;
+    cout << "sv2=" << sv2 << endl;
+    s1[0] = 'B';
+    cout << "修改s1后" << endl;
+    cout << "s1=" << s1 << endl;
+    cout << "s2=" << s2 << endl;
+    cout << "sv1=" << sv1 << endl;
+    cout << "sv2=" << sv2 << endl;
+}