java 354.俄罗斯娃娃信封（＃1）.java

Posted 2021-05-08

public class Solution {
    private int findLess(int[] dp, int len, int target) {
        int l = 0, r = len - 1;
        while (l < r) {
            int mid = l + (r - l) / 2;
            int midNum = dp[mid];
            if (midNum == target) return mid;
            else if (midNum > target) {
                r = mid;
            } else {
                l = mid + 1; 
            }
        }
        return l;
    }
    
    public int maxEnvelopes(int[][] envelopes) {
        int len = envelopes.length;
        Arrays.sort(envelopes, new Comparator<int[]>(){
            public int compare(int[] a, int[] b) {
                if (a[0] == b[0]) {
                    //return a[1] - b[1]; [[4,5],[4,6],[6,7],[2,3],[1,1]]
                    return b[1] - a[1];
                }
                return a[0] - b[0];
            }
        });
        
        int[] dp = new int[len];
        int idx = 0;
        for (int[] e : envelopes) {
            if (idx == 0 || e[1] > dp[idx - 1]) {
                dp[idx++] = e[1];
            } else if (e[1] < dp[idx - 1]) {
                int pos = findLess(dp, idx, e[1]);
                dp[pos] = e[1];
            }
        }
        return idx;
    }
}

public class Solution {
    public int maxEnvelopes(int[][] envelopes) {
        if (   envelopes           == null
            || envelopes.length    == 0
            || envelopes[0]        == null
            || envelopes[0].length == 0){
            return 0;    
        }

        Arrays.sort(envelopes, new Comparator<int[]>(){
            @Override
            public int compare(int[] e1, int[] e2){
                return e1[0] - e2[0];
            }
        });

        int   n  = envelopes.length;
        int[] dp = new int[n];

        int ret = 0;
        for (int i = 0; i < n; i++){
            dp[i] = 1;

            for (int j = 0; j < i; j++){
                if (   envelopes[i][0] > envelopes[j][0]
                    && envelopes[i][1] > envelopes[j][1]){
                    dp[i] = Math.max(dp[i], 1 + dp[j]);    
                }
            }

            ret = Math.max(ret, dp[i]);
        }
        return ret;
    }
}