每日一题：和相同的二元子数组（双指针）唯一最小数（模拟）

LeetCode每日一题：和相同的二元子数组（哈希+前缀和&双指针）

方法一：哈希+前缀和

class Solution {
public:
    int numSubarraysWithSum(vector<int>& nums, int goal) {
        unordered_map<int, int> hash;
        int sum = 0, res = 0;
        for (int i = 0; i < nums.size(); i ++ )
        {
            hash[sum] ++ ;
            sum += nums[i];
            res += hash[sum - goal];
        }
        return res;
    }
};

Acwing每日一题：唯一最小数模拟

能尽量不开hash的时候，尽量不开hash，因为它的常数比较大

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 200010;

int n;
int w[N], cnt[N];

int main()
{
    int T;
    scanf("%d", &T);
    while (T -- )
    {
        scanf("%d", &n);
        memset(cnt, 0, (n + 1) * 4);
        for (int i = 0; i < n; i ++ )
        {
            scanf("%d", &w[i]);
            cnt[w[i]] ++ ;
        }
        int res = -1;
        for (int i = 0; i < n; i ++ )
            if (cnt[w[i]] == 1)
            {
                if (res == -1 || w[res] > w[i])
                    res = i;
            }
        if (res != -1) res ++ ;
        printf("%d\n", res);
    }
    return 0;
}