Three types of cyclic structure

Cycle structure is divided into cycle condition and cycle operation .

A circular statement should have four parts : initialization , conditional , The loop body , iteration .

while loop ：

At the beginning of recirculation , The accountant calculates once “ Boolean expression ” Value , If the condition is true , Execution loop body . And for every subsequent extra frontal circulation , Will be calculated again before starting again .

There should be statements in the statement that make the loop tend to end , Otherwise, there will be an infinite loop -----“ die ” loop

do-while loop ：

Execute it once and judge whether it is correct at the beginning

while And do-while The difference between ： An execution before judgment , A judge before execution .do-while Always ensure that the loop body is executed at least once . therefore while Execute before judge ,do-while Judge before you execute .

for loop ：

for Loop is a general structure that supports iteration , Is the most effective , Is the most flexible loop structure

Grammatical form ：

for（ Initial expression ; Boolean expression ; Walk ）{

The loop body

}

matters needing attention ：

for After the loop performs the conditional test , Do the program first , And then step ;

stay for The variables declared in the initialization part of the statement , Its scope is the whole for The loop body ;

“ initialization ” and “ Loop expression ” Part can use commas to perform multiple operations ;

If all three parts are empty （ A semicolon ; Energy saving ）, It's like an infinite loop ;

Multiple cycles ：

Three cycles :while,do-while,for

Multiple cycles （ Nested loop ）

         A circulatory body also includes another complete circulatory structure

         Any two loops can be nested with each other

          You can loop at any level , But it usually doesn't exceed 3 layer

Multiple loop execution process ： The multi-layer cyclic variable changes once , The inner loop variable changes again

Use in multiple loops continue