**1.题目：输入某年某月某日，判断这一天是这一年的第几天？**
**2.程序分析：以3月5日为例，应该先把前两个月的加起来，然后再加上5天即本年的第几天，**
**特殊情况，闰年且输入月份大于3时需考虑多加一天。**
**3..程序源代码：**
```go
package main
import "fmt"
func main() {
var year, mouth, day, sum, feb int
fmt.Println("请输入年月日：")
fmt.Scan(&year, &mouth, &day)
if (year%4 == 0 && year%100 != 0) || (year%400 == 0) {
feb = 29
} else {
feb = 28
}
switch mouth {
case 1:
sum = 0 + day
case 2:
sum = 31 + day
case 3:
sum = feb + 31 + day
case 4:
sum = 31 + feb + 31 + day
case 5:
sum = 30 + 31 + feb + 31 + day
case 6:
sum = 31 + 30 + 31 + feb + 31 + day
case 7:
sum = 30 + 31 + 30 + 31 + feb + 31 + day
case 8:
sum = 31 + 30 + 31 + 30 + 31 + feb + 31 + day
case 9:
sum = 31 + 31 + 30 + 31 + 30 + 31 + feb + 31 + day
case 10:
sum = 30 + 31 + 31 + 30 + 31 + 30 + 31 + feb + 31 + day
case 11:
sum = 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31 + feb + 31 + day
case 12:
sum = 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31 + feb + 31 + day
}
fmt.Printf("您输入的日期是这一年的第%d天", sum)
}
```
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