根据后序遍历和中序遍历求先序遍历

public static void test2(String houxu, String zhongxu) {

if (zhongxu.length() >= 1) {

String gen = houxu.substring(houxu.length() - 1, houxu.length());

// System.out.println(sumgen);

if (!sumgen.contains(gen)) {

System.out.println(gen);

}

sumgen = gen + sumgen;

int zuoweizhi = zhongxu.indexOf(gen);

String zhongxuZUO = zhongxu.substring(0, zuoweizhi);

if (zhongxuZUO.length() > 0) {

// System.out.println(houxuZUO);

String houxuZUO = houxu.substring(0, zhongxuZUO.length());

// System.out.println(xianxuZUO);

test2(houxuZUO, zhongxuZUO);

}

String zhongxuYOU = zhongxu.substring(zuoweizhi + 1);

if (zhongxuYOU.length() > 0) {

// System.out.println(houxuYOU);

String houxuYOU = houxu.substring(zhongxuZUO.length(), houxu.length() - 1);

// System.out.println(xianxuYOU);

test2(houxuYOU, zhongxuYOU);

}

}

}

试了几个都可以不知道还有没有别的问题