# include & ltstdio.h & gt
int?main()?
{int?s=0,I,n,t = 1;
scanf("%d ",& ampn);?
for(I = 1;我& lt= n;i++)?//效率高,時間復雜度為O(n)
{ t * = I;
s+= t;
}
printf("%d\n ",s);?
}?
程序2:
# include & ltstdio.h & gt//調用函數效率低,時間復雜度為O(n ^ 2)(O(n)累加,計算階乘O(n),嵌套)。
int?事實(int?n)
{int?y = 1;
而(n)y * = n-;
回歸?y;
}
int?main()?
{int?s=0,I,n;
scanf("%d ",& ampn);?
for(I = 1;我& lt= n;i++)?
s+=事實(I);
printf("%d\n ",s);?
}