'commit'

TangDou/LuoGuBook/P3397_2.cpp

@@ -0,0 +1,42 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const int N = 1010;
+int a[N][N];
+int b[N][N];
+int n, m;
+
+/**
+ * 功能：二维差分的模板
+ * @param x1
+ * @param y1
+ * @param x2
+ * @param y2
+ * @param c
+ */
+void insert(int x1, int y1, int x2, int y2, int c) {
+    b[x1][y1] += c;
+    b[x2 + 1][y1] -= c;
+    b[x1][y2 + 1] -= c;
+    b[x2 + 1][y2 + 1] += c;
+}
+
+int main() {
+    cin >> n >> m;
+    while (m--) {
+        int x1, y1, x2, y2;
+        cin >> x1 >> y1 >> x2 >> y2;
+        //对比二维差分的表示，四个加法运算，优化掉双重循环
+        insert(x1, y1, x2, y2, 1);
+    }
+
+    //通过二维差分，还原成原始数组
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            a[i][j] = a[i - 1][j] + a[i][j - 1] - a[i - 1][j - 1]+b[i][j];
+            printf("%d ", a[i][j]);
+        }
+        printf("\n");
+    }
+    return 0;
+}