Relive C + + (ii)

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format Control characters :

%x: Output or read in 16 binary form;

%u: Unsigned output or read-in

Cin cout and scanf printf, a program do not mix the two;

operators : Assignment operators, arithmetic operators, relational operators, logical operators;

Assignment operator: =,+=,-=,*=,/=,%=

Arithmetic operators: +,-, *,/,%,++,--arithmetic operations, if there is overflow, then the overflow part is taken off (floating point type of unpredictable), such as int i=0xffffffff,j;j=i+3; J=0X100000002;J is of type int, 4 bytes, j=2; Note that calculations may not overflow, but there is overflow in the middle of the calculation, such as the calculation of printf ("%d", (A+B)/2), and if the result C of the A+B calculation is outside the int range, the calculation will go wrong . The type of division calculation is consistent with the type of high precision in the operand.

Relational operators: = = = = > < >= <= returns the bool type,

Logical operator:&& | |  ! Short-circuit calculation, that is, the calculation of the results can be predicted, not backward calculation;

Order of Operations : generally available () to make the precedence operation

Conditional structure: If else, there are multiple adjacent if else, else matches the nearest if,

If else is too large, the switch statement can be selected as appropriate.

switch (expression) {//Expression return type can only be integer type int, char (char type is actually ASCII value)

case constant Expression 1:

Break

case constant Expression 2

Break

....

}

Loop structure : For loop, for (expression 1; expression 2; expression 3) {statement Group; }

The expression in the For loop can be not written in all, but ";" To be preserved.

do{loop Body;} while (condition) loop, first loop in judging condition

Break: Jump out of the nearest loop body;

Continue: To the head of the loop, after the statement is not executed, if for loop, for (int i=0;i<n;i++), expression 3:i++ will execute

Array:

Definition: Type an array group name [number of elements], the number of elements must be a constant or constant expression; arrays are stored in memory continuously

T A[n] occupies a space of n*sizeof (t), Byte, array name a refers to the first address stored in the array, assuming p, A[n] stores the address p+n*sizeof (int),

Sieve method to calculate prime number:

The initialization of an array of int arr[10]={1,2,3,4} is not given the default value of binary 0,

Array subscript out-of-bounds compilation does not error, the operation may be error, because the operating system may not allow the write of out-of-bounds memory.

Two-dimensional arrays:

Two-dimensional arrays are also contiguous in memory for two-dimensional array initialization int a[2[3]={(4,5,6)}

If each row is initialized, you can write the number of rows int a[][3]={(4,5,6)}

Relive C + + (ii)