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| 1 | +/* |
| 2 | +677. Map Sum Pairs |
| 3 | +https://leetcode.com/problems/map-sum-pairs/ |
| 4 | + |
| 5 | +Implement a MapSum class with insert, and sum methods. |
| 6 | + |
| 7 | +For the method insert, you'll be given a pair of (string, integer). |
| 8 | +The string represents the key and the integer represents the value. |
| 9 | +If the key already existed, then the original key-value pair will be overridden to the new one. |
| 10 | + |
| 11 | +For the method sum, you'll be given a string representing the prefix, |
| 12 | +and you need to return the sum of all the pairs' value whose key starts with the prefix. |
| 13 | +*/ |
| 14 | +// time: 2019年02月01日 |
| 15 | + |
| 16 | +package mapsumpairs |
| 17 | + |
| 18 | +type node struct { |
| 19 | + val int |
| 20 | + next map[rune]*node |
| 21 | +} |
| 22 | + |
| 23 | +// MapSum data structure for solution. |
| 24 | +type MapSum struct { |
| 25 | + root *node |
| 26 | +} |
| 27 | + |
| 28 | +// Constructor initialize data structure here. |
| 29 | +func Constructor() MapSum { |
| 30 | + return MapSum{&node{next: make(map[rune]*node)}} |
| 31 | +} |
| 32 | + |
| 33 | +// Insert inserts a word into the trie. |
| 34 | +func (ms *MapSum) Insert(key string, val int) { |
| 35 | + cur := ms.root |
| 36 | + for _, c := range key { |
| 37 | + if _, ok := cur.next[c]; !ok { |
| 38 | + cur.next[c] = &node{next: make(map[rune]*node)} |
| 39 | + } |
| 40 | + cur = cur.next[c] |
| 41 | + } |
| 42 | + cur.val = val |
| 43 | +} |
| 44 | + |
| 45 | +// Sum sum of all the pairs' value whose key starts with the prefix. |
| 46 | +func (ms *MapSum) Sum(prefix string) int { |
| 47 | + cur := ms.root |
| 48 | + for _, c := range prefix { |
| 49 | + if _, ok := cur.next[c]; !ok { |
| 50 | + return 0 |
| 51 | + } |
| 52 | + cur = cur.next[c] |
| 53 | + } |
| 54 | + return sum(cur) |
| 55 | +} |
| 56 | + |
| 57 | +func sum(n *node) int { |
| 58 | + res := n.val |
| 59 | + for _, nextNode := range n.next { |
| 60 | + res += sum(nextNode) |
| 61 | + } |
| 62 | + return res |
| 63 | +} |
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