Swift-第一个只出现一次的字符

题目：在一个字符串中找到第一个只出现一次的字符。如输入abaccdeff，则输出b.
核心代码:
<pre><code>`

func findFirstStr(string:String) -> String {
    var str:String = string
    var dict:[String:Int] = [:]
    for i in 0..<str.characters.count {
        let char:String = str[i]
        if dict.keys.contains(char) {
            let count:Int = dict[char]!
            dict[char] = count + 1
        } else {
            dict[char] = 1
        }
    }
    var result:String = ""
    for i in 0..<str.characters.count {
        let char:String = str[i]
        if dict[char]! == 1 {
            result = char
            break
        }
    }
    return result
}`</code></pre>

测试代码:
<pre><code>var hashSearch:HashSearch = HashSearch() var firstChar:String = hashSearch.findFirstStr(string: "简简单单的FlyElephant") print("第一次只出现一次的字符---\(firstChar)")</code></pre>