试题D 数的分解

 答案：40785

#include <iostream>
using namespace std;

bool check(int i) {
    int x;
    while (i) {
        x = i % 10;
        if (x == 2 || x == 4)
            return false;
        i /= 10;
    }
    return true;
}

/*
条件约束：
    1.各整数不相等
    2.每个整数不含2或4
    3.不能有重复的(j=j+1;k=k+1避免不重复)
*/
int main() {
    int n = 2019, count = 0, k;
    for (int i = 1; i < 2000; i++) {
        if (check(i)) {
            for (int j = i + 1; j < 2000; j++) {
                if (check(j) && j != i) {
                    for (int k = j + 1; k < 2000; k++) {
                        if (check(k) && k != i && k != j && i + j + k == 2019) {
                            count++;
                        }
                    }
                }
            }
        }
    }
    cout << count;
    return 0;
}