总算过了,看了题解才知道是因为重复的不算,比如 1 + 4、4 + 1、2 + 3、3 + 2 都是重复,也就是结果相同的不同的两个数只能出现一组。于是加上判断就好。
#include <bits/stdc++.h> #define rep(i, a, b) for(int i = a; i <= b; i++) #define min(a, b) ((a) < (b) ? (a) : (b)) #define max(a, b) ((a) > (b) ? (a) : (b)) #define ll long long #define N 200005 int gcd(int a, int b){return b == 0 ? a : gcd(a%b, a);} int a[N], vis[N]; int top = 0; int main(int n, char**v) { scanf("%d", &n); for (int i = 0; i < N; vis[i++] = 0); for (int i = 0; i < n; i++) { scanf("%d", &a[i]); vis[a[i]] = 1; } for (int i = 0; i < n; i++) for (int j = i + 1; j < n; j++) if (vis[a[i] + a[j]] && vis[a[i] + a[j]] != 2) vis[a[i] + a[j]] = 2, top++; printf("%d ", top); return 0; }