题目

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.
s = "loveleetcode",
return 2.

Note: You may assume the string contain only lowercase letters.

解题思路

1. 如果字符串为空，直接返回-1
2. 遍历字符串，将字符串中的字符放入map中，字符第一次出现，值为字符所在位置，字符再次出现，值为字符串长度（也可以其他较大值）
3. 遍历map，寻找位置最小值minPos
4. 如果minPos等于字符串长度，说明所有字符都重复，返回-1，否则minPos即为所求第一个非重复字符的位置

代码

findUniqueChar.go

package _387_First_Unique_Character_String

import "fmt"

func FirstUniqChar(s string) int {
    len1 := len(s)
    if 0 == len1 {
        return -1
    }
    var charMap map[byte]int
    charMap = make(map[byte]int)


    for i := 0; i < len1; i++ {
        _, ok := charMap[s[i]]

        if ok {
            charMap[s[i]] = len1
        } else {
            charMap[s[i]] = i
        }
    }

    fmt.Printf("map:%+v\n", charMap)

    var minPos int
    minPos = len1
    for _, v := range charMap {
        if minPos > v {
            minPos = v
        }
    }

    if len1 == minPos {
        return -1
    }
    return minPos
}

测试

findUniqueChar_test.go

package _387_First_Unique_Character_String

import "testing"

func TestFirstUniqChar(t *testing.T) {
    var tests = []struct{
        intput string
        output int
    }{
        {"loveleetcode", 2},
        {"", -1},
        {"cc", -1},
    }

    for _, test := range tests {
        ret := FirstUniqChar(test.intput)

        if ret == test.output {
            t.Logf("pass")
        } else {
            t.Errorf("fail, want %+v, get %+v", test.output, ret)
        }
    }
}