for语句和switch语句分别实现

前言

用两种不同的方法求解【输入某年某日，判断这是这一年的第几天】

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一、用switch做

代码如下（示例）：

int main()
{int y, m, d, count, k;scanf("%d %d %d", &y, &m, &d);if ((y % 4 == 0 && y % 100 != 0) || y % 400 == 0)k = 1;else k = 0;count = d;switch (m - 1){case 11:count = count + 30;case 10:count = count + 31;case 9:count = count + 30;case 8:count = count + 31;case 7:count = count + 31;case 6:count = count + 30;case 5:count = count + 31;case 4:count = count + 30;case 3:count = count + 31;case 2:count = count + 28+k;case 1:count = count + 31;}printf("%d年%d月%d日是%d年的第%d天", y, m, d, y, count);return 0;
}

该处不能把count=d放在switch里面，switch语句执行时会先匹配case，若放在switch语句里面，会报错，出现未初始化变量count

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如下代码及运行结果：

二、用for循环做

代码如下（示例）：

int main()
{int i,y, m, d, countday, k;int mouth[12] = { 0,31,28,31,30,31,30,31,31,30,31,30 };scanf("%d %d %d", &y, &m, &d);if ((y % 4 == 0 & y % 10 != 0) || y % 400 == 0)k = 1;else k = 0;mouth[2] = mouth[2] + k;countday = d;for (i = 1; i < m; i++)countday = countday + mouth[i];printf("%d年%d月%d日是%d年的第%d天", y, m, d, y, countday);return 0;
}

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如下代码及运行结果： 

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总结