前n项和！
就当是练习了（各种高精度）！综合很强！
View Code
#include
"
iostream
"
#define
M 1010
using
namespace
std;
char
ch1[M],ch2[M];
int
a[M],b[M];
int
c[M],d[M];
int
num[M];
int
sum[M];
int
W[M];
int
H[M];
int
t,k,g,v;
int
i,j;
int
La,Lb;
int
sign
=
0
;
int
s;
int
L;
void
_ADD()
{
La
=
0
;
W[La
++
]
=
(sum[L
-
1
]
+
1
)
%
10
;
int
flag
=
(sum[L
-
1
]
+
1
)
/
10
;
int
i;
for
(i
=
L
-
2
;i
>=
0
;i
--
)
{
W[La
++
]
=
(sum[i]
+
flag)
%
10
;
flag
=
(sum[i]
+
flag)
/
10
;
}
while
(flag)
{
W[La
++
]
=
flag
%
10
;
flag
/=
10
;
}
}
void
Div(
int
*
xx)
{
Lb
=
0
;
int
sign
=
0
;
for
(
int
i
=
0
;i
<
L;i
++
)
{
if
((xx[i]
+
sign)
>=
2
)
{
b[Lb
++
]
=
(xx[i]
+
sign)
/
2
;
sign
=
(xx[i]
-
2
*
(xx[i]
/
2
));
}
else
{
sign
=
xx[i]
*
10
;
if
(i) b[Lb
++
]
=
0
;
}
}
}
void
Add(
int
x ,
int
y)
{
sign
=
0
; t
=
0
;
int
p,q,flag
=
0
;
if
(x
>
y)
{
for
(p
=
0
,q
=
0
;p
<
y,q
<
y; p
++
,q
++
)
{
num[t
++
]
=
(d[p]
+
H[q]
+
flag)
%
10
;
flag
=
(d[p]
+
H[q]
+
flag)
%
10
;
}
for
(p
=
y; p
<
x ; p
++
)
{
num[t
++
]
=
(d[p]
+
flag)
%
10
;
flag
=
(d[p]
+
flag)
/
10
;
}
}
else
if
(x
==
y)
{
for
(p
=
0
,q
=
0
;p
<
x,q
<
y; p
++
,q
++
)
{
num[t
++
]
=
(d[p]
+
H[q]
+
flag)
%
10
;
flag
=
(d[p]
+
H[q]
+
flag)
/
10
;
}
}
else
{
flag
=
0
;
for
(p
=
0
,q
=
0
;p
<
x,q
<
x; p
++
,q
++
)
{
num[t
++
]
=
(H[p]
+
d[q]
+
flag)
%
10
;
flag
=
(H[p]
+
d[q]
+
flag)
/
10
;
}
for
(q
=
x;q
<
y;q
++
)
{
num[t
++
]
=
(H[q]
+
flag)
%
10
;
flag
=
(H[q]
+
flag)
/
10
;
}
}
while
(flag)
{
num[t
++
]
=
flag
%
10
;
flag
/=
10
;
}
for
(
int
yy
=
0
; yy
<
t;yy
++
)
{
d[yy]
=
num[yy];
if
(d[yy]
==
0
) sign
++
;
//
sign用于标记结果为0的情况
}
g
=
t;
memset(H ,
0
,
sizeof
(H));
memset(num,
0
,
sizeof
(num));
}
void
BigN()
{
int
flag
=
0
;
int
mark
=
0
;
if
(La
>
Lb)
{
for
(i
=
Lb
-
1
;i
>=
0
;i
--
)
{
k
=
0
;
for
(j
=
La
-
1
;j
>=
0
;j
--
)
{
c[k
++
]
=
(b[i]
*
a[j]
+
flag)
%
10
;
flag
=
(b[i]
*
a[j]
+
flag)
/
10
;
}
while
(flag)
{
c[k
++
]
=
flag
%
10
;
flag
/=
10
;
}
//
末尾赋值0
v
=
0
;
for
(
int
xx
=
0
; xx
<
mark; xx
++
)
H[v
++
]
=
0
;
for
(
int
m
=
0
;m
<
k;m
++
)
H[v
++
]
=
c[m];
memset(c,
0
,
sizeof
(c));
Add(g , v);
mark
++
;
}
}
else
{
for
(i
=
La
-
1
;i
>=
0
;i
--
)
{
k
=
0
;
for
(j
=
Lb
-
1
;j
>=
0
;j
--
)
{
c[k
++
]
=
(a[i]
*
b[j]
+
flag)
%
10
;
flag
=
(a[i]
*
b[j]
+
flag)
/
10
;
}
while
(flag)
{
c[k
++
]
=
flag
%
10
;
flag
/=
10
;
}
//
末尾赋值0
v
=
0
;
for
(
int
xx
=
0
; xx
<
mark; xx
++
)
H[v
++
]
=
0
;
for
(
int
m
=
0
;m
<
k;m
++
)
H[v
++
]
=
c[m];
Add(g , v);
mark
++
;
}
}
}
int
main()
{
while
(cin
>>
ch1)
{
t
=
0
;k
=
0
;g
=
0
;
L
=
strlen(ch1);
for
(i
=
0
;i
<
L;i
++
) { sum[i]
=
ch1[i]
-
'
0
'
;}
_ADD();
if
(W[La
-
1
]
%
2
==
0
)
{
for
(i
=
0
;i
<
L;i
++
) a[i]
=
ch1[i]
-
'
0
'
;
L
=
La; Div(W);
}
else
{
for
(i
=
0
;i
<
La;i
++
) a[i]
=
W[i];
Div(sum);
}
BigN();
if
(sign
!=
t)
{
for
(i
=
t
-
1
;i
>=
0
;i
--
)
cout
<<
d[i];
cout
<<
endl;
}
else
cout
<<
"
0
"
<<
endl;
}
return
0
;
}