提高组B1第三讲回文构造机
题目链接
#include <bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
const int N = 1005;
map<char, int> mp;
int n, oddnum = 0, evennum = 0;
char odd[30], even[30];
char s[N];
signed main () {
ios::sync_with_stdio(false);
cin.tie();
cout.tie();
cin >> (s + 1);
n = strlen(s + 1);
for (int i = 1; i <= n; i++) {
mp[s[i]]++;
}
for (char i = 'a'; i <= 'z'; i++) {
if (mp[i] != 0) {
if (mp[i] % 2 == 0) {
even[++evennum] = i;
} else {
odd[++oddnum] = i;
}
}
}
if (oddnum == 0) {
cout << 1 << endl;
} else {
cout << oddnum << endl;
}
for (int i = 1; i <= evennum; i++) {
for (int j = 1; j <= mp[even[i]] / 2; j++) {
cout << even[i];
}
}
for (int j = 1; j <= mp[odd[1]]; j++) {
cout << odd[1];
}
for (int i = evennum; i >= 1; i--) {
for (int j = 1; j <= mp[even[i]] / 2; j++) {
cout << even[i];
}
}
cout << endl;
for (int i = 2; i <= oddnum; i++) {
for (int j = 1; j <= mp[odd[i]]; j++) {
cout << odd[i];
}
cout << endl;
}
return 0;
}
问为什么样例1和样例3过不了??? 
