738.单调递增的数字

遇到了strNum[i - 1] > strNum[i]，让strNum[i - 1]--，然后strNum[i]及以后给为9

根据这种情况从后往前遍历

class Solution {public int monotoneIncreasingDigits(int n) {String s = String.valueOf(n);char[] chars = s.toCharArray();int start = s.length();for (int i = s.length() - 2; i >= 0; i--) {if (chars[i] > chars[i + 1]) {chars[i]--;start = i+1;}}for (int i = start; i < s.length(); i++) {chars[i] = '9';}return Integer.parseInt(String.valueOf(chars));}
}

贪心算法总结：

没有固定套路，更多是记忆