贪心

# 860. 柠檬水找零 - 力扣（LeetCode） (opens new window)

class Solution {
    public boolean lemonadeChange(int[] bills) {
        int crash_5 = 0;
        int crash_10 = 0;
        for(int i = 0; i < bills.length; i++){
            if (bills[i] == 5){
                crash_5++;
            } else if (bills[i] == 10){
                crash_5--;
                crash_10++;
            } else if (bills[i] == 20){
                if(crash_10 > 0){
                    crash_10--;
                    crash_5--;
                } else {
                    crash_5 -= 3;
                }
            }
            if (crash_5 < 0 || crash_10 < 0) return false;       
         }
         return true;
    }
}

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# 56. 合并区间 - 力扣（LeetCode） (opens new window)

class Solution {
    public int[][] merge(int[][] intervals) {
        if (intervals.length == 0) return new int[0][2];
        Arrays.sort(intervals, (a, b) -> a[0] - b[0]);
        List<int[]> merged = new ArrayList<>();
        merged.add(intervals[0]);
        for (int i = 1; i < intervals.length; i++) {
            int[] last = merged.get(merged.size() - 1);
            if (intervals[i][0] > last[1]) {
                merged.add(intervals[i]);
            } else {
                last[1] = Math.max(intervals[i][1], last[1]);
            }
        }
        return merged.toArray(new int[merged.size()][]);
    }
}

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# 179. 最大数 - 力扣（LeetCode） (opens new window)

class Solution {
    public String largestNumber(int[] nums) {
        String[] strs = new String[nums.length];
        for (int i = 0; i < nums.length; i++) {
            strs[i] = String.valueOf(nums[i]);
        }
        // a+b 与 b+a 的字典序比较 定义排序规则，是贪心思想的典型应用
        Arrays.sort(strs, (a, b) -> (b + a).compareTo(a + b));
        // 如 "00" 需转为 "0"
        if (strs[0].equals("0")) return "0";
        return String.join("", strs);
    }
}

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编辑

上次更新: 2025/07/25, 12:08:10

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