139. 单词拆分

首先要明确这个是求排列数，所以是先遍历背包，再遍历物品。

func wordBreak(s string, wordDict []string) bool {
    dp := make([]bool, len(s) + 1)
    dp[0] = true
    for j := 1; j <= len(s); j++{
        for i := 0; i < len(wordDict); i++{
        
            if j - len(wordDict[i]) >= 0 && dp[j - len(wordDict[i])] == true && wordDict[i] == s[(j - len(wordDict[i])) : j]{
                dp[j] = true
            }

        } 
    }
    return dp[len(s)]
}