nt/pythagorean_triple.hpp

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• Last update: 2026-08-17 09:25:20+09:00
• Include: #include "nt/pythagorean_triple.hpp"
• Link: https://codeforces.com/contest/60/problem/D

Verified with

• test/1_mytest/pythagorean_triples.test.cpp

Code

/*
c <= LIM, (a,b,c) と (b,a,c) は同一視, O(LIM) 時間
・LIM = 10^8：互いに素 1.59*10^7 個, 0.13sec
・LIM = 10^8：全部 2.71*10^8 個, 0.53sec
https://codeforces.com/contest/60/problem/D
*/
template <bool coprime_only, typename F>
void enumerate_pythagorean_triple(int LIM, F f) {
  vc<tuple<int, int, int>> que;
  auto add = [&](int a, int b, int c) -> void {
    if (c <= LIM) que.eb(a, b, c);
  };
  add(3, 4, 5);
  while (len(que)) {
    auto [a, b, c] = POP(que);
    add(a - 2 * b + 2 * c, 2 * a - b + 2 * c, 2 * a - 2 * b + 3 * c);
    add(a + 2 * b + 2 * c, 2 * a + b + 2 * c, 2 * a + 2 * b + 3 * c);
    add(-a + 2 * b + 2 * c, -2 * a + b + 2 * c, -2 * a + 2 * b + 3 * c);
    if constexpr (coprime_only) {
      f(min(a, b), max(a, b), c);
    } else {
      int x = min(a, b), y = max(a, b), z = c;
      while (z <= LIM) {
        f(x, y, z);
        x += min(a, b), y += max(a, b), z += c;
      }
    }
  }
}

#line 1 "nt/pythagorean_triple.hpp"

/*
c <= LIM, (a,b,c) と (b,a,c) は同一視, O(LIM) 時間
・LIM = 10^8：互いに素 1.59*10^7 個, 0.13sec
・LIM = 10^8：全部 2.71*10^8 個, 0.53sec
https://codeforces.com/contest/60/problem/D
*/
template <bool coprime_only, typename F>
void enumerate_pythagorean_triple(int LIM, F f) {
  vc<tuple<int, int, int>> que;
  auto add = [&](int a, int b, int c) -> void {
    if (c <= LIM) que.eb(a, b, c);
  };
  add(3, 4, 5);
  while (len(que)) {
    auto [a, b, c] = POP(que);
    add(a - 2 * b + 2 * c, 2 * a - b + 2 * c, 2 * a - 2 * b + 3 * c);
    add(a + 2 * b + 2 * c, 2 * a + b + 2 * c, 2 * a + 2 * b + 3 * c);
    add(-a + 2 * b + 2 * c, -2 * a + b + 2 * c, -2 * a + 2 * b + 3 * c);
    if constexpr (coprime_only) {
      f(min(a, b), max(a, b), c);
    } else {
      int x = min(a, b), y = max(a, b), z = c;
      while (z <= LIM) {
        f(x, y, z);
        x += min(a, b), y += max(a, b), z += c;
      }
    }
  }
}

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