题目链接
https://www.patest.cn/contests/pat-a-practise/1041
思路
可以用 map 标记 每个数字的出现次数 然后最后再 遍历一遍 找到那个 第一个 第一次出现的数字
AC代码
#include <cstdio> #include <cstring> #include <ctype.h> #include <cstdlib> #include <cmath> #include <climits> #include <ctime> #include <iostream> #include <algorithm> #include <deque> #include <vector> #include <queue> #include <string> #include <map> #include <stack> #include <set> #include <numeric> #include <sstream> #include <iomanip> #include <limits> #define CLR(a) memset(a, 0, sizeof(a)) #define pb push_back using namespace std; typedef long long ll; typedef long double ld; typedef unsigned long long ull; typedef pair <int, int> pii; typedef pair <ll, ll> pll; typedef pair<string, int> psi; typedef pair<string, string> pss; const double PI = 3.14159265358979323846264338327; const double E = exp(1); const double eps = 1e-30; const int INF = 0x3f3f3f3f; const int maxn = 1e5 + 5; const int MOD = 1e9 + 7; int main() { int n, num; scanf("%d", &n); map <int, int> m; vector <int> ans; for (int i = 0; i < n; i++) { scanf("%d", &num); m[num]++; if (m[num] == 1) ans.pb(num); } vector <int>::iterator it; for (it = ans.begin(); it != ans.end(); it++) { if (m[*it] == 1) { printf("%d\n", *it); break; } } if (it == ans.end()) printf("None\n"); }转载于:https://www.cnblogs.com/Dup4/p/9433196.html
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