poj 2408 Anagram Groups(hash)

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题目大意：给定若干个字符串，将其分组，依照组成元素同样为一组，输出数量最多的前5组，每组依照字典序输出所

有字符串。数量同样的输出字典序较小的一组。

解题思路：将全部的字符串统计字符后hash。排序之后确定每组的个数而且确定一组中字典序最小的字符串。依据个数

以及字符串对组进行排序。

#include <cstdio>
#include <cstring>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;
const int maxn = 30005;
const int maxm = 30;
const int X = 30;
typedef unsigned long long ll;
typedef pair<ll,int> pii;
int N, M, E;
vector<pii> vec, grop;
vector<int> g[maxn];
char word[maxn][maxm], st[maxn][maxm];
inline ll Hash(char* s) {
int len = strlen(s), c[maxm];
memset(c, 0, sizeof(c));
for (int i = 0; i < len; i++)
c[s[i]-'a']++;
ll ret = 0;
for (int i = 0; i < 26; i++)
ret = ret * X + c[i];
return ret;
}
inline bool cmp (const pii& a, const pii& b) {
if (a.second == b.second)
return strcmp(st[a.first], st[b.first]) < 0;
return a.second > b.second;
}
inline bool sort_by(const int& a, const int& b) {
return strcmp(word[a], word[b]) < 0;
}
int main () {
N = M = E = 0;
vec.clear();
grop.clear();
while (scanf("%s", word[N]) == 1) {
ll key = Hash(word[N]);
vec.push_back(make_pair(key, N));
N++;
}
sort(vec.begin(), vec.end());
int cnt = 0;
ll pre = -1;
for (int i = 0; i < vec.size(); i++) {
int idx = vec[i].second;
if (vec[i].first != pre) {
if (cnt)
grop.push_back(make_pair(M++, cnt));
cnt = 0;
g[M].clear();
pre = vec[i].first;
strcpy(st[M], word[idx]);
}
cnt++;
g[M].push_back(idx);
if (strcmp(word[idx], st[M]) < 0)
strcpy(st[M], word[idx]);
}
if (cnt)
grop.push_back(make_pair(M++, cnt));
sort(grop.begin(), grop.end(), cmp);
for (int i = 0; i < min(5, (int)grop.size()); i++) {
printf("Group of size %d: ", grop[i].second);
int x = grop[i].first;
sort(g[x].begin(), g[x].end(), sort_by);
for (int j = 0; j < g[x].size(); j++) {
if (j == 0 || strcmp(word[g[x][j-1]], word[g[x][j]]))
printf("%s ", word[g[x][j]]);
}
printf(".\n");
}
return 0;
}