Bài giảng Tin học đại cương A: Control Structures - Nguyễn Dũng

Control Structures Nguyen Dung Falculty of Information Technology Hue University of Science Content Selection if statement switch statement Iteration (loop) for statement while statement do while statement Jump: break continue return goto 2 if statement Syntax 1st: if ( expression ) {B;} exp B nonzero zero 3 if statement Example: int a = 5, b = 9, max; max = a; if ( max < b ){ max = b;} printf(“Max is: %d”,max); Max is: 9 if (max < b) max = b; 4 if statement Syntax 2nd: if ( exp ) {B1;} else {B2;} exp B1 nonzero zero B2 5 if statement float a, b, x; printf(“a = ");scanf("%f",&a); printf(“b = ");scanf("%f",&b); if (a == 0 ){ if ( b != 0 ) printf(“Equation hasn’t root.”); else printf(“Equation has countless root.”); } else{ x = -b/a; printf(“Root of equation is x = %f”,x); } a = 2 b = 6 Root of equation is x = -3.00 6 Excercises 1. Xác định xem một số nguyên là chẵn hay lẻ. 2. Xác định học lực dựa vào điểm trung bình của sinh viên, biết: 3. Xác định số có giá trị lớn hơn trong hai số thực a, b theo 2 cách: sử dụng lệnh if và không sử dụng lệnh if 4. Hiển thị một số tự nhiên bất kì từ 0 đến 9 dưới dạng chữ. ĐTB [0, 4) [4, 5) [5, 6.5) [6.5, 8) [8, 9) [9, 10] Học lực Kém Yếu Trung bình Khá Giỏi Xuất sắc 7 exp== exp1 exp== exp2 exp== expn B0; B1; B2; Bn; Zero Zero Zero Zero Non-Zero Non-Zero Non-Zero 8 switch statement Syntax: switch (exp) { case (exp1): B1; break; case (exp2): B2; break; ... case (expN): BN; break; [default: B0;] } expression Constant-expression 9 Example: void main() { int x; printf("Nhap so: "); scanf("%d", &x); switch(x){ case 0: printf(“Khong”);break; case 1: printf(“Mot”);break; case 2: printf(“Hai”);break; case 3: printf(“Ba”);break; case 4: printf(“Bon”);break; case 5: printf(“Nam”);break; case 6: printf(“Sau”);break; case 7: printf(“Bay”);break; case 8: printf(“Tam”);break; case 9: printf(“Chin”);break; } getch(); } Nhap so: 6 Sau 10 while .. do statement Syntax: while (exp) { B; } exp B; Zero Non-Zero 11 Example Find “greatest common divisor” of a and b. Then find “least common multiple” of a and b Input: a, b Output: GCD(a,b) and LCM(a,b) Method: 𝐺𝐶𝐷 𝑎, 𝑏 = 𝑎 𝑖𝑓 𝑏 = 𝑎 𝐺𝐶𝐷 𝑎 − 𝑏, 𝑏 𝑖𝑓 𝑎 > 𝑏 𝐺𝐶𝐷 𝑎, 𝑏 − 𝑎 𝑖𝑓 𝑎 < 𝑏 𝐺𝐶𝐷 𝑎, 𝑏 = 𝑎𝑏 𝐿𝐶𝑀 (𝑎, 𝑏) 𝐺𝐶𝐷 𝑎, 𝑏 = 𝑎 𝑖𝑓 𝑏 = 0 𝐺𝐶𝐷 𝑏, 𝑏 𝑚𝑜𝑑 𝑎 𝑖𝑓𝑏 ≠ 0 12 Implement unsigned int x, y, a, b; printf("Nhap x, y: "); scanf("%d,%d", &x, &y); if (x == 0 && y == 0) printf(“Both a and b are 0\n"); else if (x * y == 0){ printf(“GCD(%d,%d) is: %d\n", x, y, x+y); } else{ a = x;b = y; while(a != b){ if (a > b) a -= b; else b -= a; } printf(“GCD(%d,%d): %d\n", x, y, a); printf(“LCM(%d,%d) is: %d\n",x, y,(x*y)/a); } unsigned int r = 0; while(b!=0){ r = a % b; a = b; b = r; } 13 do .. while statement Syntax: do { B; } while (exp); exp B; Zero Non-Zero Different with while statement??? 14 Example #include #include void main() { int x; char c; do{ printf(“\nEnter x: ”); scanf(“%f”, &x); if (x%2==0){ printf(“%d is even”,x); } else printf(“%d is odd”,x); printf(“\nPress ESC to exit... ”); c = getch(); } while (c!=27); } Enter x: 6 6 is even Press ESC to exit... Enter x: 7 7 is odd Press ESC to exit... 15 for statement Syntax: for(exp0;exp1;exp2) { B; } exp1 exp0; Zero Non-Zero B; exp2; 16 Example Find the following sum: S = 1 + 2 + 3 + ... + n = 𝒊𝒏𝒊=𝟏 Input: n Output: sum of n number from 1 to n Method: s = 0; For i = 1 to n do s = s + i; 17 Implement #include #include void main() { int n, s=0; printf(“Enter n: "); scanf("%d", &n); for(int i = 1; i <= n; i++) s = s + i; printf(“Sum is: ", s); getch(); } Enter n: 6 Sum is: 21 18 break, continue, goto The break command allows you to terminate and exit a loop (that is, do, for, and while) or switch command from any point Example int s = 0; for(int i = 0; i <= 10; i++){ if (i == 5) break; s = s + i; } printf(“s = %d”,s); s= ??? 19 break, continue, goto The continue statement jumps the next loop. Example int s = 0; for(int i = 0; i <= 10; i++){ if (i == 5) continue; s = s + i; } printf(“s = %d”,s); S = ??? 20 break, continue, goto Goto: self-study 21 return The return statement: terminates the execution of a function or return a result(address or value) to the calling function and exit function. Syntax: return exp; 22 Warning Homework Please visit website to get it. 23 Questions 24 The end 25