题解 | 硬币凑钱

#include <stdio.h>

int main(void) {
    int n;
    scanf("%d", &n);

    int k7 = n / 7;
    int r = n % 7;
    int ans;

    if (r == 0) {
        ans = k7;
    } else if (r == 1) {
        ans = k7 + 1;
    } else if (r == 2) {
        ans = k7 + 2;
    } else if (r == 3) {
        if (k7 >= 1) {
            ans = k7 - 1 + 2;
        } else {
            ans = k7 + 3;
        }
    } else if (r == 4) {
        if (k7 >= 1) {
            ans = k7 - 1 + 3;
        } else {
            ans = k7 + 4;
        }
    } else if (r == 5) {
        ans = k7 + 1;
    } else if (r == 6) {
        ans = k7 + 2;
    }
    printf("%d", ans);
    return 0;
}