全网首个不用map的解法！！！

为了改bug我还花了一次机会看测试点😭

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
//#include <map>
using namespace std;
int a[200005], b[200005], bucket[200005], ctb;
int find(int left, int right, int val, int *a){//分治查找
	if(a[left] == val) return left;
	if(a[right] == val) return right;
	if(a[left] > val || a[right] < val) return 0;
	int mid = (left + right) >> 1;
	return max(find(left, mid, val, a), find(mid + 1, right, val, a));
}
int read(){//快读
	char c = getchar();
	int x = 0;
	while(!isdigit(c)) c = getchar();
	while(isdigit(c)){
		x = (x << 3) + (x << 1) + c - '0';
		c = getchar();
	}return x;
}
int main(){
	b[0] = -1;
	int n = read(), m = read();
	for(int i = 1; i <= n; i++){
		a[i] = read();
	}sort(a + 1, a + n + 1);//sort
	for(int i = 1; i <= n; i++){
		if(b[ctb] != a[i]) b[++ctb] = a[i];//记录有多少种数字
	}
	for(int i = 1; i <= n; i++){
		bucket[find(1, ctb, a[i], b)]++;//记录每种数字的个数
	}
	long long ct = 0;
	for(int i = 1; i <= ctb; i++){
		if(b[i] >= m){
			int idx = find(1, ctb, b[i] - m, b);
			ct += bucket[idx] * 1ll * bucket[i];//计算
		}
	}
	cout << ct;

	return 0;
}

时间复杂度：$O(n\log_2n)$