107年普考程式設計概要

二、請問以下程式輸出的結果為何?(10分)

#include <iostream>

#include <cstdlib>

using namespace std;

int main(void) {

int i = 0, sum = 0;

while(i < 21) {

if(i%3 != 0) {

i++;

continue;

}

sum += i++;

}

cout << "i = " << i << ", SUM = " << sum << endl;

return 0;

}

答:

#include <iostream>

#include <cstdlib>

using namespace std;

int main(void) {

    int i = 0, sum = 0;

    while (i < 21) {

        if (i % 3 != 0) {

            i++;

            continue;

        }

        sum += i++;

    }

    cout << "i = " << i << ", SUM = " << sum << endl;

    return 0;

}

執行結果:

i = 21, SUM = 63

說明:

i = 0 時,sum = sum+i = 0+0 = 0

i = 1 時,i++ = 2

i = 2 時,i++ = 3

i = 3 時,sum = sum+i = 0+3 = 3

i = 4 時,i++ = 5

i = 6 時,sum = sum+i = 3+6 = 9

i = 9 時,sum = sum+i = 9+9 = 18

i = 12 時,sum = sum+i = 18+12 = 30

i = 15 時,sum = sum+i = 30+15 = 45

..

i = 18 時,sum = sum+i = 45+18 = 63

 

 

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