題目連結

https://www.acwing.com/problem/content/900/

題目思路

這道題我們可以從最底層考慮，若要使當前路徑之和最大，選擇當前的所選值加左上/右上之和最大即可
因為有負數情況，所以要把邊界設定好

題目程式碼

#include <iostream>
#include <algorithm>

using namespace std;
const int INF = 0x3f3f3f3f;
const int N = 510;
int a[N][N], f[N][N];
int n;

int main()
{
    cin >> n;
    for(int i = 1; i <= n; i ++ )
        for(int j = 1; j <= i; j ++ )
            cin >> a[i][j];
            
    for(int i = 0; i <= n; i ++ )
        for(int j = 0; j <= i + 1; j ++ )   
            f[i][j] = -INF;
            
    f[1][1] = a[1][1];
    
    for(int i = 2; i <= n; i ++ )
        for(int j = 1; j <= i;j ++ )
            f[i][j] = max(f[i - 1][j - 1] + a[i][j], f[i - 1][j] + a[i][j]);
    
    int res = -INF;
    for(int i = 1; i <= n; i ++ )
        res = max(res, f[n][i]);
        
    cout << res << endl;
    return 0;
    
}