平方数计数

#include <iostream>
using namespace std;

int main() {
    int a, b;
    cin >> a >> b;
    int cnt = 0;
    for (int i = 1; i * i <= b; i++) {
        if (i * i >= a) cnt++;
    }
    cout << cnt;
    return 0;
}

数字矩阵和

#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    int sum = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            cout << i * j;
            if (j != n) cout << " ";
            sum += i * j;
        }
        cout << endl;
    }
    cout << "Sum=" << sum << endl;
    return 0;
}

数位递增的数

#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    int cnt = 0;

    for (int i = 1; i <= n; i++) {
        int x = i;
        int last = 10; // 初始为比最高位大的数
        bool ok = true;
        while (x > 0) {
            int now = x % 10;
            if (now >= last) {
                ok = false;
                break;
            }
            last = now;
            x /= 10;
        }
        if (ok) cnt++;
    }
    cout << cnt;
    return 0;
}