677. 键值映射

https://leetcode-cn.com/problems/map-sum-pairs/

• 提交时间:2021-11-13 18:37:50
• 执行用时：0 ms, 在所有 Go 提交中击败了100.00%的用户
• 内存消耗：2.7 MB, 在所有 Go 提交中击败了64.41%的用户
• 通过测试用例：35 / 35

type MapSum struct {
    stage map[string]int
    pre   map[string]int
}

func Constructor() MapSum {
    return MapSum{stage: make(map[string]int), pre: make(map[string]int)}
}

func (m *MapSum) Insert(key string, val int) {
    if oldVal, ok := m.stage[key]; ok {
        if oldVal == val {
            return
        }
        for i := 1; i <= len(key); i++ {
            m.pre[key[0:i]] += (val - oldVal)
        }
        m.stage[key] = val
        return
    }
    for i := 1; i <= len(key); i++ {
        m.pre[key[0:i]] += val
    }
    m.stage[key] = val
}

func (m *MapSum) Sum(prefix string) int {
    return m.pre[prefix]
}

/**
 * Your MapSum object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Insert(key,val);
 * param_2 := obj.Sum(prefix);
 */