lanqiao 2109 统计子矩阵(二维前缀和)

13lanqiao/test6-1.cpp

@@ -0,0 +1,36 @@
+// lanqiao 2109 统计子矩阵(二维前缀和)
+#include<bits/stdc++.h>
+using namespace std;
+#define int long long
+const int N = 5e2 + 10;
+int n, m, k;
+int a[N][N], sum[N][N];
+// 暴力解法，枚举子矩阵，二维前缀和求矩阵和，时间复杂度 O(n^4)
+signed main(){
+    cin >> n >> m >> k;
+    for(int i = 1; i <= n; i++){
+        for(int j = 1; j <= m; j++){
+            cin >> a[i][j];
+            sum[i][j] = sum[i-1][j] + sum[i][j-1] - sum[i-1][j-1] + a[i][j];
+        }
+    }
+    int ans = 0, res;
+    for(int i = 1; i <= n; i++){
+        for(int j = 1; j <= m; j++){
+            for(int i1 = i; i1 <= n; i1++){
+                for(int j1 = j; j1 <= m; j1++){
+                    res  = sum[i1][j1] - sum[i-1][j1] - sum[i1][j-1] + sum[i-1][j-1];
+                    if(res <= k) ans++;
+                }
+            }
+        }
+    }
+    cout << ans << endl;
+    return 0;
+}
+/* samples -> 19
+3 4 10
+1 2 3 4
+5 6 7 8
+9 10 11 12
+*/