英文:
Why is while loop inside a for loop entering into an infinite loop?
问题
当我尝试运行这段代码时，它进入了一个无限循环，如果有人能解释一下，然后最后的条件语句永远不会被执行。我试图打印出从1到500的阿姆斯特朗数。如果有人能调试它并给我正确的代码，或者至少帮我了解这里发生了什么。
while循环陷入无限循环。for(int s=1; s<=500; s++){//System.out.println(i);int total=0;while(s != 0) {//System.out.println(s);int digit = s % 10;//System.out.println(digit+" "+s);total = total+(digit*digit*digit);//System.out.println(total);//reversed = reversed*10 + digit;s = s/10;//System.out.println(s);}if (total==s) {System.out.println(s);}}
英文:
While loop entering into infinite loop.
for(int s=1; s<=500; s++){//System.out.println(i);int total=0;while(s != 0) {//System.out.println(s);int digit = s % 10;//System.out.println(digit+" "+s);total = total+(digit*digit*digit);//System.out.println(total);//reversed = reversed*10 + digit;s = s/10;//System.out.println(s);}if (total==s) {System.out.println(s);}}
When i try to run this it enters into an infinite loop, if anyone can explain it and then the last if never gets executed. I am trying to print armstrong numbers from 1 to 500. If anyone can debug it and give me the correct code or at least help me get to know what is going on here.
答案1
得分: 0
你正在在另一个循环内部修改循环变量 s。这就是你陷入无限循环的原因。在这里使用一个临时变量会更有意义。
修正后的代码：
for (int s = 1; s <= 500; s++) {int total = 0;int temp = s; // 使用临时变量while (temp != 0) {int digit = temp % 10;total = total + (digit * digit * digit);temp = temp / 10;}if (total == s) {System.out.println(s);}}
在这个代码示例中，temp 在循环的每次迭代中保存了 s 的值。现在，它每次被除以 10 次，不会改变 s 的值。if 语句 if (total == s) 现在应该能够正常工作。
英文:
You are changing the variable s of the loop inside another loop.
This is the reason why you get an infinite loop. Using a temporary variable would make sense here.
Fixed Code:
for (int s = 1; s <= 500; s++) {int total = 0;int temp = s; // Use temp variablewhile (temp != 0) {int digit = temp % 10;total = total + (digit * digit * digit);temp = temp / 10;}if (total == s) {System.out.println(s);}}
In this example of code temp is holding the value of s for each iteration of the loop. Now it gets divided 10x every time leaving s unchanged. The if-clause if (total == s) should work correctly now.
答案2
得分: 0
你不应该改变循环变量 s：s=s/10。请使用临时变量代替：
for (int s = 1; s <= 500; s++) {int total = 0;int q = s;while (q != 0) {int digit = q % 10;total = total + (digit * digit * digit);q = q / 10;}if (total == s) {System.out.println(s);}}
英文:
You should not change the cycle variable s: s=s/10. Use the temporary variable instead:
for(int s=1; s<=500; s++){//System.out.println(i);int total=0; int q = s;while(q != 0) {//System.out.println(s);int digit = q % 10;//System.out.println(digit+" "+q);total = total+(digit*digit*digit);//System.out.println(total);//reversed = reversed*10 + digit;q = q/10;//System.out.println(s);}if (total==s) {System.out.println(s);}}
答案3
得分: 0
我相信while循环不会无限循环，因为s/10会返回0（请记住这都是整数，而在整数中1/10 = 0）。
然而，for循环将会无限循环，因为每次通过while循环时，您都将s设置为0，然后for循环中的指令会将其增加1，因此s在每次for循环的迭代中都变为1。
至于if语句，它不会执行，因为在您的代码中total = total+(digit*digit*digit);其中digit = s % 10导致1，因此在if条件中您将得到一个条件1 == 0，这将始终评估为false。
英文:
I believe while loop will not be infinite because s/10 will return 0 (keep in mind it's all integer and in integer 1/10 = 0).
The for loop however will be infinite because each time you run through the while loop you set s to 0 and then the instruction in the for loop increments it by 1, so s ends up being 1 in every iteration of the for loop.
As for the if statement, it does not execute because in your code total = total+(digit*digit*digit); where digit = s % 10 that results to 1, hence in the if condition you'll end up with a condition 1 == 0 that will always evaluate to false
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