当心变量发生上溢或下溢

当心变量发生上溢或下溢，数组的下标越界。

 1 #include <iostream>
 2 #include <stack>
 3 
 4 
 5 using namespace std ;
 6 
 7 typedef stack<int> STACK_INT;
 8 /* run this program using the console pauser or add your own getch, system("pause") or input loop */
 9 
10 int main(int argc, char** argv) {
11         STACK_INT stack1;
12     int i;
13 
14     //判断栈是否空
15     cout << "stack1.empty() returned " <<
16          (stack1.empty()? "true": "false") << endl;  
17 
18     //0,2,4,6...入栈
19     for (i=0;i<10;i=i+2)
20         stack1.push(i);
21 
22     //top()函数
23     if (!stack1.empty())                         
24         cout << "stack1.top() returned " <<stack1.top() << endl;
25  
26     //计算栈的长度
27     cout<<"stack1.size(): "<<stack1.size()<<endl;
28    
29     //改变栈顶的值 20.
30     if (!stack1.empty()) {                        
31         cout << "stack1.top()=20;" << endl;
32         stack1.top()=20;                         
33     }
34 
35     //弹出栈中所有的数据并显示
36     cout<<"stack1: ";
37     while (!stack1.empty()) {                   
38         cout<<stack1.top()<<" ";
39         stack1.pop();
40     }
41     cout<<endl;
42     return 0;
43 }