C++ for循环如何排除一些循环值？

Question

for(int i=0;i<10;i++)
    for (int j=0;j<10;j++)

怎么实现第二个for循环里只产生不同于i的值？
比如i==0时，j取1到9；

Answer 1

In fact, it can be like this... When the number of loops is very large, it is more effective; because if you make a judgment once in each loop, it will be judged as many times as there are loops. It is better to skip this judgment directly.

const int max = 10;

for (int i = 0; i < max; i++) {
    for (int j = 0; j < i; j++) {
        // call function to do something
    }
    for (int j = i + 1; j < max; j++) {
        // call function to do something
    }
}

Answer 2

if(i==j)continue;

Answer 3

You can use it in two ways, one is @sin’s kind

for(int i=0;i<10;i++){
    for (int j=0;j<10;j++){
        if(i==j){
            continue;
        }
        //Paste your code here.
    }
}

Another way is:

for(int i=0;i<10;i++){
    for (int j=0;j<10;j++){
        if(i==j){
            //Do nothing.
        }
        else{
            //Paste your code here.
        }
    }
}

The former is more concise, especially when the logic is particularly complex, the advantages of the former are better reflected.

Answer 4

@sin’s answer is very good and the efficiency is also reflected.