一本通1622：Goldbach’s Conjecture

最新推荐文章于 2025-12-02 10:59:15 发布

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#c++ #算法

本文介绍了一个使用C++编写的程序，它读取输入，找出每个输入数字的最小质因数，并输出分解后的结果。程序中包含内联函数，如读取整数、写入数字和处理素数分解。

#include <stdio.h>
#include <ctype.h>
#include <string.h>
#define maxN 1000000
using namespace std;

inline long long read(long long x = 0, bool flag = 0, char c = 0) {
    for (c = getchar(); !isdigit(c); c = getchar())
        if (c == '-')
            flag = 1;

    for (; isdigit(c); x = (x << 3) + (x << 1) + (c ^ 48), c = getchar());

    return (flag) ? -x : x;
}
inline void write(long long x) {
    if (x > 9)
        write(x / 10);

    putchar(x % 10 + 48);
}
inline void writeln(long long x) {
    if (x < 0)
        putchar('-'), write(-x);
    else
        write(x);
}

int minprime[maxN + 3], prime[maxN / 4], m = 0;
inline void primes(int n) {
    memset(minprime, 0, sizeof(minprime));

    for (register int i = 2; i <= n; i++) {
        if (!(minprime[i]))
            minprime[i] = i, prime[++m] = i;

        for (register int j = 1; j <= m; j++)
            if (prime[j] > minprime[i] || i * prime[j] > n)
                break;
            else
                minprime[i * prime[j]] = prime[j];
    }
}

int main() {
    primes(1000000);

    for (register int i = read(); i; i = read())
        for (register int j = 1; j <= m; j++)
            if (minprime[i - prime[j]] == i - prime[j]) {
                writeln(i), putchar(' '), putchar('='), putchar(' '), writeln(prime[j]), putchar(' '), putchar('+'),
                        putchar(' '), writeln(i - prime[j]), puts("");
                break;
            }

    return 0;
}