Question

编写程序判断两个数组是否相等，然后编写一段类似的程序比较两个vector。

#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> ivec1, ivec2;
int ival;
//读入两个vector 的元素值
cout << "Enter numbers for vector1(-1 to end):" << endl;
cin >> ival;
while (ival != -1) {
ivec1.push_back(ival);
cin >> ival;
}
cout << "Enter numbers for vector2(-1 to end):" << endl;
cin >> ival;
while (ival != -1) {
ivec2.push_back(ival);
cin >> ival;
}
//判断两个vector 是否相等
if (ivec1.size() != ivec2.size()) //长度不等的vector 不相等
cout << "Vector1 is not equal to vector2." << endl;
else if (ivec1.size() == 0) //长度都为0 的vector 相等
cout << "Vector1 is equal to vector2." << endl;
else {//两个vector 长度相等且不为0
vector<int>::iterator iter1, iter2;
iter1 = ivec1.begin();
iter2 = ivec2.begin();
while (*iter1 == *iter2 && iter1 != ivec1.end()
&& iter2 != ivec2.end()) {
++iter1;
++iter2;
}
if (iter1 == ivec1.end())//所有元素都相等
cout << "Vector1 is equal to vector2." << endl;

else
cout << "Vector1 is not equal to vector2." << endl;
}
system("pause");
return 0;
}
cout << "Enter numbers for vector1(-1 to end):" << endl;
cin >> ival;
while (ival != -1) {
ivec1.push_back(ival);
cin >> ival;
}
为什么 有两次 cin>>ival;
不理解谢谢

Answer 1

已改，看注释

#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> ivec1, ivec2;
int ival;
//读入两个vector 的元素值
cout << "Enter numbers for vector1(-1 to end):" << endl;
cin >> ival;
while (ival != -1) {
ivec1.push_back(ival);
cin >> ival;
}
cout << "Enter numbers for vector2(-1 to end):" << endl;
cin >> ival;
while (ival != -1) {
ivec2.push_back(ival);
cin >> ival;
}
//判断两个vector 是否相等
if (ivec1.size() != ivec2.size()) //长度不等的vector 不相等
cout << "Vector1 is not equal to vector2." << endl;
else if (ivec1.size() == 0) //长度都为0 的vector 相等
cout << "Vector1 is equal to vector2." << endl;
else {//两个vector 长度相等且不为0
vector<int>::iterator iter1, iter2;
iter1 = ivec1.begin();
iter2 = ivec2.begin();
while (iter1 != ivec1.end() && *iter1 == *iter2) { // 先判断是不是end()，不是才判断是否相等
++iter1;
++iter2;
}
if (iter1 == ivec1.end())//所有元素都相等
cout << "Vector1 is equal to vector2." << endl;
else
cout << "Vector1 is not equal to vector2." << endl;
}
system("pause");
return 0;
}

追问

cout > ival;
while (ival != -1) {
ivec1.push_back(ival);
cin >> ival;
}
为什么 有两次 cin>>ival;
不理解谢谢

追答

第一次是先输入一次，然后以此判断输入的是否为-1，不是-1的就push_back，然后再继续输入，再判断

追问

if (if (iter1 == ivec1.end())//所有元素都相等
为什么 iter1 == ivec1.end()) 所有元素都相等
？？谢谢 麻烦了

追答

因为
while (iter1 != ivec1.end() && *iter1 == *iter2) { // 先判断是不是end()，不是才判断是否相等
++iter1;
++iter2;
}
这个判断就是，假如没到ivec1的结尾或者有元素相等，就继续循环，直到结尾。如果没到结尾就退出了循环，证明有元素不相等，因此用iter1 == ivec1.end()) 来判断是否所有元素相等