chore: add rust code

Author: yanglbme

solution/1500-1599/1504.Count Submatrices With All Ones/README.md

@@ -228,6 +228,44 @@ function numSubmat(mat: number[][]): number {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn num_submat(mat: Vec<Vec<i32>>) -> i32 {
+        let m = mat.len();
+        let n = mat[0].len();
+        let mut g = vec![vec![0; n]; m];
+
+        for i in 0..m {
+            for j in 0..n {
+                if mat[i][j] == 1 {
+                    if j == 0 {
+                        g[i][j] = 1;
+                    } else {
+                        g[i][j] = 1 + g[i][j - 1];
+                    }
+                }
+            }
+        }
+
+        let mut ans = 0;
+        for i in 0..m {
+            for j in 0..n {
+                let mut col = i32::MAX;
+                let mut k = i as i32;
+                while k >= 0 && col > 0 {
+                    col = col.min(g[k as usize][j]);
+                    ans += col;
+                    k -= 1;
+                }
+            }
+        }
+        ans
+    }
+}
+```
+
 #### JavaScript
 
 ```js