Acwing 3487. 最小面积子矩阵 && 3505. 最长ZigZag子序列

៚ོ朝夕ོོ ͜✿ ҉҉҉҉҉2023-09-21 22:34

思路：二维矩阵前缀和，暴力枚举最小值

cpp 复制代码

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

const int M = 110;
int g[M][M];

int main() {
    int n, m, k;
    cin >> n >> m >> k;
    for (int i = 1; i <= n; i ++) {
        for (int j = 1; j <= m; j ++) {
            cin >> g[i][j];
            g[i][j] += g[i - 1][j] + g[i][j - 1] - g[i - 1][j - 1];
        }
    }
    
    int res = INT_MAX;
    
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            for(int x = i; x <= n; x++){
                for(int y = j; y <= m; y++) {
                    int sum = g[x][y] - g[i - 1][y] - g[x][j - 1] + g[i - 1][j - 1];
                    if(sum >= k) {
                        res = min(res, (x - i + 1) * (y - j + 1));
                    }
                }
            }
        }
    }
    if(res == INT_MAX) {
        cout << -1 << endl;
    }else {
        cout << res << endl;
    }
    return 0;
}

3505. 最长ZigZag子序列 - AcWing题库

cpp 复制代码

#include <iostream>
using namespace std;

const int N = 60;
int nums[N];
int dp[N][2];

int main() {
    int n = 0;
    cin >> n;
    for(int i = 1; i <= n; i++) {
        cin >> nums[i];
    }

    for(int i = 1;i <= n; i++){
        dp[i][0] = 1;
        dp[i][1] = 1;
        for(int j = 1;j < i; j++){
            if(nums[i] > nums[j])   dp[i][1] = max(dp[i][1], dp[j][0]+1);
            if(nums[i] < nums[j])   dp[i][0] = max(dp[i][0], dp[j][1]+1);
        }
    }
    cout << max(dp[n][0], dp[n][1]) << endl;
    return 0;
}