feat: 添加P7074题解，实现动态规划解法

src/9/13/P7074.cpp

@@ -0,0 +1,47 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+
+using namespace std;
+
+const long long INF = -1e18;
+
+int main() {
+
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int n, m;
+    cin >> n >> m;
+
+    vector<vector<int>> a(n + 1, vector<int>(m + 1));
+    for (int i = 1; i <= n; ++i) {
+        for (int j = 1; j <= m; ++j) {
+            cin >> a[i][j];
+        }
+    }
+
+    vector<vector<long long>> dp(n + 2, vector<long long>(m + 2, INF));
+
+    dp[1][0] = 0;
+
+    for (int j = 1; j <= m; ++j) {
+
+        for (int i = 1; i <= n; ++i) {
+            dp[i][j] = dp[i][j - 1] + a[i][j];
+        }
+
+        for (int i = 2; i <= n; ++i) {
+            dp[i][j] = max(dp[i][j], dp[i - 1][j] + a[i][j]);
+        }
+
+        for (int i = n - 1; i >= 1; --i) {
+            dp[i][j] = max(dp[i][j], dp[i + 1][j] + a[i][j]);
+        }
+    }
+
+    cout << dp[n][m] << endl;
+
+    return 0;
+}