优化原题解，添加部分题目

problems/0454.四数相加II.md

@@ -18,14 +18,19 @@
 **例如:**
 
 输入:
-A = [ 1, 2]
-B = [-2,-1]
-C = [-1, 2]
-D = [ 0, 2]
+* A = [ 1, 2]
+* B = [-2,-1]
+* C = [-1, 2]
+* D = [ 0, 2]
+
 输出:
+
 2
+
 **解释:**
+
 两个元组如下:
+
 1. (0, 0, 0, 1) -> A[0] + B[0] + C[0] + D[1] = 1 + (-2) + (-1) + 2 = 0
 2. (1, 1, 0, 0) -> A[1] + B[1] + C[0] + D[0] = 2 + (-1) + (-1) + 0 = 0