C++ primer-练习3.34~3.36

3.34：假定P1和P2指向同一个数组中的元素，则下面程序的功能是什么？什么情况下非法？

P1+=P2-P1;

功能是让p1指向目前所指元素后第p2-p1个元素。只有当p1为常量指针是，才非法。

3.35：编写程序，利用指针将数组中元素置为零。

3.36：编写程序，比较两个数组是否相等，比较2个vector是否相等。

#include<iostream>#include<vector>using namespace std;int main(){int p = 0,q=0;constexpr size_t i = 5;int a[i] = { 1,2,3,4,5 }, b[i] = { 1,3,4,5,6 };if (sizeof(a) != sizeof(b))cout << "arrays are not equal!"<<endl;else{for (int t = 0; t != i; t++){if (a[t] != b[t])p++;}}if (p == 0)cout << "arrays are equal!" << endl;elsecout << "arrays are not equal!" << endl;vector<int> p1{ 1,2,3,4,5 }, p2{1,3,4,5,6};if(p1.size()!=p2.size())cout<<"vectors are not equal!" << endl;else{vector<int>::iterator ip1 = p1.begin(), ip2 = p2.begin();for (decltype(p1.size()) i = 0; i != p1.size(); i++){if (*(ip1++) !=* (ip2++))q++;}}if (q == 0)cout << "vectors are equal!" << endl;elsecout << "vectors are not equal!" << endl;return 0;}