Add solution 0677

leetcode/0677.Map-Sum-Pairs/677. Map Sum Pairs.go

@@ -0,0 +1,43 @@
+package leetcode
+
+type MapSum struct {
+	keys map[string]int
+}
+
+/** Initialize your data structure here. */
+func Constructor() MapSum {
+	return MapSum{make(map[string]int)}
+}
+
+func (this *MapSum) Insert(key string, val int) {
+	this.keys[key] = val
+}
+
+func (this *MapSum) Sum(prefix string) int {
+	prefixAsRunes, res := []rune(prefix), 0
+	for key, val := range this.keys {
+		if len(key) >= len(prefix) {
+			shouldSum := true
+			for i, char := range key {
+				if i >= len(prefixAsRunes) {
+					break
+				}
+				if prefixAsRunes[i] != char {
+					shouldSum = false
+					break
+				}
+			}
+			if shouldSum {
+				res += val
+			}
+		}
+	}
+	return res
+}
+
+/**
+ * Your MapSum object will be instantiated and called as such:
+ * obj := Constructor();
+ * obj.Insert(key,val);
+ * param_2 := obj.Sum(prefix);
+ */

leetcode/0677.Map-Sum-Pairs/README.md

@@ -0,0 +1,100 @@
+# [677. Map Sum Pairs](https://leetcode.com/problems/map-sum-pairs/)
+
+
+## 题目
+
+Design a map that allows you to do the following:
+
+- Maps a string key to a given value.
+- Returns the sum of the values that have a key with a prefix equal to a given string.
+
+Implement the `MapSum` class:
+
+- `MapSum()` Initializes the `MapSum` object.
+- `void insert(String key, int val)` Inserts the `key-val` pair into the map. If the `key` already existed, the original `key-value` pair will be overridden to the new one.
+- `int sum(string prefix)` Returns the sum of all the pairs' value whose `key` starts with the `prefix`.
+
+**Example 1:**
+
+```
+Input
+["MapSum", "insert", "sum", "insert", "sum"]
+[[], ["apple", 3], ["ap"], ["app", 2], ["ap"]]
+Output
+[null, null, 3, null, 5]
+
+Explanation
+MapSum mapSum = new MapSum();
+mapSum.insert("apple", 3);
+mapSum.sum("ap");           // return 3 (apple = 3)
+mapSum.insert("app", 2);
+mapSum.sum("ap");           // return 5 (apple +app = 3 + 2 = 5)
+
+```
+
+**Constraints:**
+
+- `1 <= key.length, prefix.length <= 50`
+- `key` and `prefix` consist of only lowercase English letters.
+- `1 <= val <= 1000`
+- At most `50` calls will be made to `insert` and `sum`.
+
+## 题目大意
+
+实现一个 MapSum 类，支持两个方法，insert 和 sum：
+
+- MapSum() 初始化 MapSum 对象
+- void insert(String key, int val) 插入 key-val 键值对，字符串表示键 key ，整数表示值 val 。如果键 key 已经存在，那么原来的键值对将被替代成新的键值对。
+- int sum(string prefix) 返回所有以该前缀 prefix 开头的键 key 的值的总和。
+
+## 解题思路
+
+- 简单题。用一个 map 存储数据，Insert() 方法即存储 key-value。Sum() 方法即累加满足条件前缀对应的 value。判断是否满足条件，先根据前缀长度来判断，只有长度大于等于 prefix 长度才可能满足要求。如果 key 是具有 prefix 前缀的，那么累加上这个值。最后输出总和即可。
+
+## 代码
+
+```go
+package leetcode
+
+type MapSum struct {
+	keys map[string]int
+}
+
+/** Initialize your data structure here. */
+func Constructor() MapSum {
+	return MapSum{make(map[string]int)}
+}
+
+func (this *MapSum) Insert(key string, val int) {
+	this.keys[key] = val
+}
+
+func (this *MapSum) Sum(prefix string) int {
+	prefixAsRunes, res := []rune(prefix), 0
+	for key, val := range this.keys {
+		if len(key) >= len(prefix) {
+			shouldSum := true
+			for i, char := range key {
+				if i >= len(prefixAsRunes) {
+					break
+				}
+				if prefixAsRunes[i] != char {
+					shouldSum = false
+					break
+				}
+			}
+			if shouldSum {
+				res += val
+			}
+		}
+	}
+	return res
+}
+
+/**
+ * Your MapSum object will be instantiated and called as such:
+ * obj := Constructor();
+ * obj.Insert(key,val);
+ * param_2 := obj.Sum(prefix);
+ */
+```