hdu 2058 The sum problem 枚举区间长度 + 等差公式

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <functional>
#include <vector>
#include <map>
#include <set>
using namespace std;

typedef long long ll;

int main()
{
ll n, m;

while(scanf("%I64d%I64d", &n, &m), n != 0 || m != 0)
{
int cnt = sqrt(2 * m); // 对于最长连续和的长度cnt, cnt(1 + cnt) / 2 = m, 于是求得cnt
while(cnt)
{
int l = (2 * m / cnt - cnt + 1) / 2; //由等差数列求和公式变形可得，当区间长度为cnt时，求得左端边界
int r = l + cnt - 1;
if(cnt * (l + r) / 2 == m)
printf("[%d,%d]\n", l, r);
cnt--;
}

printf("\n");
}

return 0;
}