'commit'

TangDou/Topic/PrefixAndSuffix/P1719.cpp

@@ -8,13 +8,14 @@ int main() {
     for (int i = 1; i <= n; i++)
         for (int j = 1; j <= n; j++) {
             cin >> a[i][j];
-            s[i][j] = s[i - 1][j] + a[i][j];
+            s[i][j] = s[i - 1][j] + a[i][j]; // 利用一维前缀和，把当前第j列前面的1~j-1列的值，累加和压缩到第j列，每列都是如此处理
         }
 
-    for (int i = 1; i <= n; ++i) {
-        for (int j = 0; j < i; ++j) {
+    // O(N^3)算法
+    for (int i = 1; i <= n; i++) {
+        for (int j = 0; j < i; j++) {
             int _s = 0;
-            for (int k = 1; k <= n; ++k) {
+            for (int k = 1; k <= n; k++) {
                 _s = max(_s, 0) + s[i][k] - s[j][k];
                 res = max(res, _s);
             }