int sum = 0;
for (int i=13, j=1; i<=1003; i+=10; j*=-1) {
    sum += (i*j);
}
System.out.println(sum);

------解决方案--------------------
Java code
public static void getNum() {
        int sun = 0;
        boolean open = true;
        for (int i = 13; i <= 1003; i += 10) {
            if (open) {
                if (i == 13)
                    sun = i;
                else {
                    sun = sun - i;
                    open = false;
                }
            } else {
                sun = sun + i;
                open = true;
            }
        }
        System.out.println(sun);
    }

------解决方案--------------------
Java code
int sum = 0;
for (int i=13, j=1; i<=1003; i+=10, j*=-1) { //上面这里写错了，是[，]不是[；]
    sum += (i*j);
}
System.out.println(sum);

------解决方案--------------------
探讨


for example
Java code
int sum = 0;
for (int i=13, j=1; i<=1003; i+=10; j*=-1) {
    sum += (i*j);
}
System.out.println(sum);


------解决方案--------------------
探讨


Java code
public static void getNum() {
        int sun = 0;
        boolean open = true;
        for (int i = 13; i <= 1003; i += 10) {
            if (open) {
                if (i == 13)
        ……


------解决方案--------------------
探讨


Java code
int sum = 0;
for (int i=13, j=1; i<=1003; i+=10, j*=-1) { //上面这里写错了，是[，]不是[；]
    sum += (i*j);
}
System.out.println(sum);

结果是-500


------解决方案--------------------
Java code
public static void main(String[] args) {
        int j=0;
        for(int i=0;i<1004;i++){
            if((""+i).endsWith("3")){
                j+=i;
            }
        }
        System.out.println(j);
    }

------解决方案--------------------
结果是 50803

------解决方案--------------------
Java code
public static void main(String[] args) {
        int j=1;
        int count=0;
        boolean flag=false;
        for(int i=13;i<1004;i++){
            if((""+i).endsWith("3")){
                if(count%2==0){
                    flag=true;
                }
                if(count%2!=0){
                    flag=false;
                }
                if(flag){
                    j-=i;
                    count++;
                }
                else{
                    j+=i;
                    count++;
                }
            }
        }
        System.out.println(j);
    }