判断区间是否重叠（Leetcode 252）

public static boolean canAttendMeetings(int[][] intervals) {//按照会议开始时间排序Arrays.sort(intervals, (a, b) ->  a[0] - b[0]);for (int i = 0; i < intervals.length - 1; i++) {if (intervals[i + 1][0] <= intervals[i][1]) {return false;}}return true;}

插入区间（LeetCode 57）

/*** 先把结尾处小于新增区间初始的加入到ans* 对重复/新增区间做判断* 把开始点大于上一节点后的节点加入到ans* @param intervals* @param newInterval* @return*/public static int[][] insert(int[][] intervals, int[] newInterval) {int[][] ans = new int[intervals.length + 1][2];int t = 0;int i = 0;// 先把结尾处小于新增区间初始的加入到answhile (i < intervals.length && intervals[i][1] < newInterval[0]) {ans[t++] = intervals[i++];}// 对重复/新增区间做判断while (i < intervals.length && intervals[i][0] <= newInterval[1]) {newInterval[0] = Math.min(intervals[i][0], newInterval[0]);newInterval[1] = Math.max(intervals[i++][1], newInterval[1]);}ans[t++] = newInterval;// 把开始点大于上一节点后的节点加入到answhile (i < intervals.length && intervals[i][0] > newInterval[1]) {ans[t++] = intervals[i++];}return Arrays.copyOf(ans, t);}

字符串分割（LeetCode 763）

public static List<Integer> partitionLabels(String S) {List<Integer> list = new LinkedList<>();char[] chars = S.toCharArray();int[] edges = new int[26];for (int i = 0; i < chars.length; i++){edges[chars[i] - 'a'] = i;}int index = 0, pre = -1;for (int i = 0; i < chars.length; i++) {index = Math.max(index, edges[chars[i] - 'a']);if (i == index) {list.add(i - pre);pre = i;}}return list;}

加油站问题（LeetCode 134）

public static int canCompleteCircuit(int[] gas, int[] cost) {int totNum = 0;int curNum = 0;int start = 0;for (int i = 0; i < gas.length; i++) {curNum += gas[i] - cost[i];totNum += gas[i] - cost[i];if (curNum < 0) {curNum = 0;start = i + 1;}}if (totNum < 0) {return -1;}return start;}