update chapter 04

Author: ShiqiYu

week02/Lecture02.pptx

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+#include <iostream>
+using namespace std;
+int main()
+{
+    int num_array1[5]; //uninitialized array, random values 
+    int num_array2[5] = {0, 1, 2, 3, 4}; //initialization
+
+    for(int idx = 0; idx < 5; idx++)
+        cout << num_array1[idx] << " ";
+    cout << endl;
+
+    for(int idx = 0; idx < 5; idx++)
+        cout << num_array2[idx] << " ";
+    cout << endl;
+}

week04/Lecture04.pptx

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+#include <iostream>
+using namespace std;
+
+//float array_sum(const float *values, size_t length)
+//float array_sum(const float values[4], size_t length)
+float array_sum(const float values[], size_t length)
+{
+    float sum = 0.0f;
+    for (int i = 0; i < length; i++)
+    {
+        sum += values[i];
+        //values[i] = 0; //error
+    }
+    return sum;
+}
+
+int main()
+{
+    // const float PI = 3.1415926f;
+    // PI += 1.f; // error
+    // const float values[4] = {1.1f, 2.2f, 3.3f, 4.4f};
+    // values[0] = 1.0f; // error
+
+    float values[4] = {1.1f, 2.2f, 3.3f, 4.4f};
+    float sum = array_sum(values, 4);
+
+    cout << "sum = " << sum << endl;
+    return 0;
+}

week04/examples/array.cpp

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+#include <iostream>
+using namespace std;
+int main()
+{
+    int num_array[5]; 
+
+    for(int idx = -1; idx <= 5; idx++) //out of bounds
+        num_array[idx] = idx * idx;
+
+    for(int idx = -1; idx <= 5; idx++) //out of bounds
+        cout << "num_array[" << idx << "] = " << num_array[idx] << endl;
+
+    return 0;
+}

week04/examples/const-array.cpp

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+#include <iostream>
+#include <cstring>
+using namespace std;
+
+int main()
+{
+    char rabbit[16] = {'P', 'e', 't', 'e', 'r'};
+    cout << "String length is " << strlen(rabbit) << endl;
+    for(int i = 0; i < 16; i++)
+        cout << i << ":" << +rabbit[i] << "(" << rabbit[i] << ")" << endl;
+
+    char bad_pig[9] = {'P', 'e', 'p', 'p', 'a', ' ', 'P', 'i', 'g'};
+    char good_pig[10] = {'P', 'e', 'p', 'p', 'a', ' ', 'P', 'i', 'g', '\0'};
+
+    cout << "Rabbit is (" << rabbit << ")" << endl;
+    cout << "Pig's bad name is (" << bad_pig << ")" << endl; 
+    cout << "Pig's good name is (" << good_pig << ")" << endl; 
+
+    char name[10] = {'Y', 'u', '\0', 'S', '.', '0'};
+    cout << strlen(name) << endl;
+    
+    return 0;
+}

week04/examples/index-bound.cpp

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+#include <iostream>
+using namespace std;
+
+// You must tell the function the bound of an array,
+// otherwise, elements cannot be accessed
+// if the array is a variable-length one, it may be difficult to know the bound
+void init_2d_array(float mat[][4], //error, arrays of unknown bound
+                    size_t rows, size_t cols)
+{
+    for (int r = 0; r < rows; r++)
+        for(int c = 0; c < cols; c++)
+            mat[r][c] =  r * c;
+}
+
+int main()
+{
+    int mat1[2][3] = {{11,12,13}, {14,15,16}};
+
+    int rows = 5;
+    int cols = 4;
+    //float mat2[rows][cols]; //uninitialized array
+    float mat2[rows][4]; //uninitialized array
+
+    //init_2d_array(mat2, rows, cols);
+
+    for (int r = 0; r < rows; r++)
+        for(int c = 0; c < cols; c++)
+            mat2[r][c] =  r * c;
+
+
+    for (int r = 0; r < rows; r++)
+    {
+        for(int c = 0; c < cols; c++)
+            cout << mat2[r][c] << " ";
+        cout << endl;
+    }
+    return 0;
+}

week04/examples/initchar.cpp

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+#include <iostream>
+#include <string>
+
+using namespace std;
+int main()
+{
+    std::string str1 = "Hello";
+    std::string str2 = "SUSTech";
+    std::string result = str1 + ", " + str2;
+
+    cout << "result = " + result << endl;
+
+    cout << "The length is " << result.length() << endl;
+
+    cout << "str1 < str2 is " << (str1 < str2) << endl;
+
+    return 0;
+}

week04/examples/md-array.cpp

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+#include <iostream>
+#include <cstring>
+using namespace std;
+
+int main()
+{
+    char str1[] = "Hello, \0CPP";
+    char str2[] = "SUSTech";
+    char result[128];
+
+    for(int i = 0; i < 16; i++)
+        cout << i << ":" << +str1[i] << "(" << str1[i] << ")" << endl;
+
+    strcpy(result, str1);
+    cout << "Result = " <<  result << endl;
+    strcat(result, str2);
+    cout << "Result = " <<  result << endl;
+
+    cout << "strcmp() = " << strcmp(str1, str2) << endl;
+
+    //strcat(str1, str2); //danger operation!
+    //cout << "str1 = " << str1 << endl;
+}

week04/examples/stdstring.cpp

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+#include <iostream>
+using namespace std;
+int main()
+{
+    int num_array1[5] = {0,1}; // fixed length array, initialized to {0,1,0,0,0}  
+    cout << "sizeof(num_array1[5]) = " << sizeof(num_array1) << endl;
+
+    int len = 1;
+    while ( len < 10 )
+    {
+        int num_array2[len]; //variable-length array
+        cout << "len = " << len;
+        cout << ", sizeof(num_array2)) = " << sizeof(num_array2) << endl;
+        len ++;
+    }
+}