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D - Staircase Sequences

分解因数，枚举

#include
   
    using namespace std;typedef long long LL;set
    
     
      > st;//(r + l)*(r - l + 1) = 2 * N;//   x   *      y     = 2 * N;//分解因子int main() {       LL N;    scanf("%lld", &N);    N *= 2;    LL res = 0;    pair
      
        t;    for(LL i = 1; i * i <= N; i++) {   					//别忘了i也要LL;        if(N % i == 0) {               LL x = i, y = N / i;            if((x + y - 1) % 2 == 0) {                   LL r = (x + y - 1) / 2;                LL l = (x - r);                t.first = l, t.second = r;                if(l <= r && st.find(t) == st.end()) {                       //printf("ok: %d %d\n", l, r);                    res ++;                    st.emplace(t);                }                swap(x, y);                l = (x - r);                t.first = l;                if(l <= r && st.find(t) == st.end()) {                       //printf("ok: %d %d\n", l, r);                    res ++;                    st.emplace(t);                }            }        }    }        printf("%lld\n", res);    return 0;}
      
     
    
   

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