Programming learning records - Lesson 4 [branch and loop statements]

Conditional statements ：if,Switch

if sentence

if sentence ：if（ Conditional expression ） sentence ; Among them, the judgment of equality should use ==.

Multiple judgment statements ,if（ Conditional expression ） sentence ;if（ Conditional expression ） sentence ; It means to judge multiple at the same time , And execute , There is no order . There is no influence on each other

if（ Conditional expression ） sentence ;else if（ Conditional expression ） sentence ;if Block and else if Blocks are mutually exclusive in nature , in other words , Once the statement 1 Has been implemented , The program will skip else if block ,else if Judgment statements and statements in blocks 2 Must be skipped . And when if When the condition in does not hold , To judge else if The statement in .

if（ Conditional expression ） sentence ;else sentence ; When if When not executed , perform else The statement in .else only else The sentence is always the one closest to him if Statements match .

switch sentence

swtich（ Integer expression ）{case： Integer constant expression sentence ;case： Integer constant expression sentence }

It should be noted that , When case When the conditions are met , The statements under all conditions after this condition will be executed sequentially , Until break until .

Loop statement

while loop

Format while( Judge the condition ) { sentence }

break： Out of the loop ;continue： End the code after executing this cycle , So let's do the next loop .

for loop

Format for( Initial value setting statement ; Judgment conditional statement ; Adjustment statement of loop condition )

break： Out of the loop ;continue： End the code after executing this cycle , So let's do the next loop .

Buffer cleanup

getchar() Read the first character of the buffer

Write into the loop to clean up the buffer

while((ch == getchar) != EOF ){;} ; Only when you return EOF, Only when the read value is empty will the loop jump , In this way, the buffer can be completely emptied .