'commit'

TangDou/Topic/PrefixAndSuffix/P1719_2.cpp

@@ -3,29 +3,26 @@ using namespace std;
 
 const int N = 330;
 int n;
-int a[N][N], dp[N];
+int a[N][N], s[N][N], dp[N];
 int res = INT_MIN;
 
 int main() {
     cin >> n;
     // 前缀和(竖直方向)
-    for (int i = 1; i <= n; i++) {
+    for (int i = 1; i <= n; i++)
         for (int j = 1; j <= n; j++) {
             cin >> a[i][j];
-            a[i][j] += a[i - 1][j];
+            s[i][j] = s[i - 1][j] + a[i][j]; // 一维前缀和，这可不是二维前缀和
         }
-    }
+
     // 降维变成一维dp
-    for (int i = 0; i <= n - 1; i++) {
-        for (int j = i + 1; j <= n; j++) {
+    for (int i = 0; i <= n - 1; i++)     // 枚举左上角
+        for (int j = i + 1; j <= n; j++) // 枚举右下角
             for (int k = 1; k <= n; k++) {
-                dp[k] = max(a[j][k] - a[i][k], dp[k - 1] + a[j][k] - a[i][k]);
+                dp[k] = max(s[j][k] - s[i][k], dp[k - 1] + s[j][k] - s[i][k]);
                 res = max(res, dp[k]);
             }
-        }
-    }
-
-    cout << res;
-
+    // 输出
+    cout << res << endl;
     return 0;
 }