1.AcWing 4203. 寻找子串

原代码：

这样写就挺好，不用补了qwq

#include<bits/stdc++.h>
using namespace std;
int main()
{
    string a;
    cin >> a;
    if(a.find("1111111")!=-1 || a.find("0000000")!=-1 ) cout << "YES";
    else cout << "NO";
    return 0;
}

2.AcWing 4204. 构造矩阵

补题代码：

0x3f大神说得就挺好 https://www.acwing.com/activity/content/code/content/2216638/

#include<bits/stdc++.h>
using namespace std;

const int N = 1010;

int a[N][N];

int main()
{
    int n;
    cin >> n;
    for (int i = 0;i < n-1;i ++)
    {
        for (int j = 0;j < n-1;j ++)
        {
            a[i][j] = ((j + i) % (n - 1)) + 1;
        }
    }
    for (int i = 0;i < n-1;i ++)
    {
        a[i][n-1] = a[n-1][i] = a[i][i];
        a[i][i] = 0;
    }
    for (int i = 0;i < n;i ++)
    {
        for (int j = 0;j < n;j ++)
            cout << a[i][j] << ' ';
        cout << endl;
    }
    return 0;
}

3.AcWing 4205. 树的增边

学了图论再来补这题。。。