diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -5,3 +5,4 @@
 
 - [数组中重复的数字](./docs/数组中重复的数字.md)
 - [不修改数组找出重复的数字](./docs/不修改数组找出重复的数字.md)
+- [替换空格](./docs/替换空格.md)
diff --git "a/docs/\346\233\277\346\215\242\347\251\272\346\240\274.md" "b/docs/\346\233\277\346\215\242\347\251\272\346\240\274.md"
new file mode 100644
index 0000000..ec04640
--- /dev/null
+++ "b/docs/\346\233\277\346\215\242\347\251\272\346\240\274.md"
@@ -0,0 +1,6 @@
+# 替换空格
+
+> 请实现一个函数，把字符串中的每个空格替换成“%20”。例如，输入“We are happy.”，则输出 “We%20are%20happy.”。
+
+## 思路分析
+