大家好我无法使用new运算符在c ++中分配内存。代码如下
#include <iostream>
#include<stack>
#include<queue>
#include<string>
using namespace std;
class cell
{
public:
unsigned short int x, y;
unsigned short int dis;
cell* parent;
string step;
cell(){}
cell(unsigned short int x, unsigned short int y, cell* parent, unsigned short int d, string s):x(x), y(y), parent(parent), dis(d), step(s){}
};
bool isinside(int i, int j, int n)
{
if(i >= 0 && i < n && j >= 0 && j < n)
return true;
return false;
}
void printShortestPath(unsigned short int n, unsigned short int i_start, unsigned short int j_start, unsigned short int i_end, unsigned short int j_end)
{
// Print the distance along with the sequence of moves.
// cout << "safe1.1";
queue<cell*> q;
bool** vis = new bool*[n+1];
cout << "safe1.2\n";
for(unsigned short int i = 0; i < n+1; i++)
*(vis+i) = new bool;
cout << "safe1.3\n";
for(unsigned short int i = 0; i < n; i++)
for(unsigned short int j = 0; j < n; j++)
vis[i][j] = false;
cout << "safe1.5\n";
cell* c;
q.push(c = new cell(i_start, j_start, NULL, 0, "0")); //**ERROR HERE**
cout << "safe1.4\n";
bool reached = false;
cell* t;
cout << "safe2\n";
while(!q.empty())
{
t = q.front();
// cout << t->x << " " << t->y << " " << t->step << " " << t << endl;
q.pop();
vis[t->x][t->y] = true;
cout << t << " ";
if(t->x == i_end && t->y == j_end)
{
reached = true;
break;
}
if(isinside(t->x-2,t->y-1,n) && !vis[t->x-2][t->y-1])
{
q.push(new cell(t->x-2,t->y-1,t,t->dis+1, "UL"));
vis[t->x-2][t->y-1] = true;
}
if(isinside(t->x-2,t->y+1,n) && !vis[t->x-2][t->y+1])
{
q.push(new cell(t->x-2,t->y+1,t,t->dis+1, "UR"));
vis[t->x-2][t->y+1] = true;
}
if(isinside(t->x,t->y+2,n) && !vis[t->x][t->y+2])
{
q.push(new cell(t->x,t->y+2,t,t->dis+1,"R"));
vis[t->x][t->y+2] = true;
}
if(isinside(t->x+2,t->y+1,n) && !vis[t->x+2][t->y+1])
{
q.push(new cell(t->x+2,t->y+1,t,t->dis+1,"LR"));
vis[t->x+2][t->y+1] = true;
}
if(isinside(t->x+2,t->y-1,n) && !vis[t->x+2][t->y-1])
{
q.push(new cell(t->x+2,t->y-1,t,t->dis+1,"LL"));
vis[t->x+2][t->y-1] = true;
}
if(isinside(t->x,t->y-2,n) && !vis[t->x][t->y-2])
{
q.push(new cell(t->x,t->y-2,t,t->dis+1,"L"));
vis[t->x][t->y-2] = true;
}
cout << t << endl;
}
cell* root = t;
if(reached)
{
cout << "safe3\n";
stack<string> st;
unsigned short int aa = 0;
while(root != NULL)
{
aa++;
st.push(root->step);
// cout << "root " << root << endl;
root = root->parent;
}
cout << aa-1 << endl;
st.pop();
while(!st.empty())
{
cout << st.top() << " ";
st.pop();
}
}
else
{
std::cout << "Impossible"; // If I add return before this it does not give error in some cases.
}
cell* r = root;
while(root)
{
root = root->parent;
delete r;
r = root;
}
return;
}
int main() {
try
{
int n;
cin >> n;
unsigned short int i_start;
unsigned short int j_start;
unsigned short int i_end;
unsigned short int j_end;
cin >> i_start >> j_start >> i_end >> j_end;
cout << "safe1\n";
printShortestPath(n, i_start, j_start, i_end, j_end);
}
catch(...)
{
cout << "Not enough memory";
}
return 0;
}
当我提供大输入示例时 100个
0 0 0 19
输出是
safe1
safe1.2
safe1.3
safe1.5
，显示的错误是
solution: malloc.c:2394: sysmalloc: Assertion `(old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)' failed.
GDB trace:
Reading symbols from solution...done.
[New LWP 14031]
Core was generated by `solution'.
Program terminated with signal SIGABRT, Aborted.
#0 0x00007f92ff084428 in __GI_raise (sig=sig@entry=6)
at ../sysdeps/unix/sysv/linux/raise.c:54
#0 0x00007f92ff084428 in __GI_raise (sig=sig@entry=6)
at ../sysdeps/unix/sysv/linux/raise.c:54
#1 0x00007f92ff08602a in __GI_abort () at abort.c:89
#2 0x00007f92ff0cc2e8 in __malloc_assert (
assertion=assertion@entry=0x7f92ff1e0150 "(old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)",
file=file@entry=0x7f92ff1dcb85 "malloc.c", line=line@entry=2394,
function=function@entry=0x7f92ff1e0998 <__func__.11509> "sysmalloc")
at malloc.c:301
#3 0x00007f92ff0d0426 in sysmalloc (nb=nb@entry=64,
av=av@entry=0x7f92ff413b20 <main_arena>) at malloc.c:2391
#4 0x00007f92ff0d1743 in _int_malloc (
av=av@entry=0x7f92ff413b20 <main_arena>, bytes=bytes@entry=48)
at malloc.c:3827
#5 0x00007f92ff0d3184 in __GI___libc_malloc (bytes=48) at malloc.c:2913
#6 0x00007f92ff6c0498 in operator new(unsigned long) ()
from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#7 0x0000000000401499 in printShortestPath (n=100, i_start=<optimized out>,
j_start=<optimized out>, i_end=0, j_end=19)
at solution.cc:38
#8 0x0000000000401018 in main () at solution.cc:135
从输出中可以清楚地看到“safe1.4”没有打印出来，所以错误似乎与评论“ERROR HERE”一致
请帮助。
答案 0 :(得分：1)
我没有详细阅读所有代码，但行：
for(unsigned short int i = 0; i < n+1; i++)
*(vis+i) = new bool;
但是，向指针添加int很可能无法提供预期的结果。见http://www.cplusplus.com/doc/tutorial/pointers/
可能会尝试：
bool* cur_vis_ptr =*vis;
for(unsigned short int i = 0; i < n+1; i++){
cur_vis_ptr=new bool;
cur_vis_ptr++;
}
或许更好的简单方法：
for(unsigned short int i = 0; i < n+1; i++)
vis[i]=new bool;