[leetcode]Bull and Cows

有时候要再三审视思路...因为未必是对的.. 最好先弄个小test case 想好思路想一想. 思路分两步走 先找matched 顺便把不match的入hash, 然后再找不match 还有一个更高效的方法是用counter...下次记得用

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public class Solution { public String getHint(String secret, String guess) { HashMap<Character, Integer> lookup = new HashMap<Character, Integer>(); int matched = 0; int hasNum = 0; for (int i = 0; i < secret.length(); i++){ char sechar = secret.charAt(i); char guchar = guess.charAt(i); if (sechar == guchar) matched++; else{ int count = 1; if (lookup.containsKey(sechar)){ count += lookup.get(sechar); } lookup.put(sechar, count); } } for (int i = 0; i < guess.length(); i++){ char guchar = guess.charAt(i); char sechar = secret.charAt(i); if (guchar != sechar && lookup.containsKey(guchar)){ int count = lookup.get(guchar)-1; if (count == 0) lookup.remove(guchar); else lookup.put(guchar, count); if (guchar == sechar) matched++; else hasNum++; } } return matched+"A"+hasNum+"B"; } }