pat1041 Be Unique

题意：

给n个数，输出第一个唯一的数。

思路：

字符串hash一下，用map维护出现次数即可。

代码

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <map>

using namespace std;

typedef unsigned long long ull;

const int MAX_S = 100;
const int MAX_N = 100000;
const ull BASE = 131;

ull hashs(char s[]) {
    int len = strlen(s);
    ull ans = 0;
    for (int i = 0; i < len; i++) {
        ans = ans * BASE + (ull)s[i];
    }
    return ans & 0x7fffffff;
}

int n;
char s[MAX_N][MAX_S];
int t[MAX_N];
map<int, int> ma;

int main() {
    // freopen("in.txt", "r", stdin);
    // freopen("out.txt", "w", stdout);
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%s", s[i]);
        t[i] = hashs(s[i]);
        ma[t[i]]++;
    }
    bool flag = false;
    for (int i = 0; i < n; i++) {
        if (ma[t[i]] == 1) {
            printf("%s\n", s[i]);
            flag = true;
            break;
        }
    }
    if (!flag) {
        printf("None\n");
    }
    return 0;
}