1007 Maximum Subsequence Sum (25point(s)) 需要二刷 *动态规划最大连续序列和，极其重要

Posted 2021-03-08 songlinxuan

基本思想关键点详见 “数据结构典型问题”

 

#include<iostream>
#include<stdlib.h>
#include<stdio.h>
#include<vector> 
#include<string>
#include<math.h>
#include<algorithm>
#include<cstring>
#include<map>
#include<queue>
#include<set>
#include<stack>
using namespace std;

int n;
vector<int>num;
vector<int>dp;
vector<int>root;
int main() {
    cin >> n;
    int st, ed;
    bool flag = true;
    //num.resize(n);
    dp.resize(n);
    root.resize(n);
    int a;
    for (int i = 0; i < n; i++) {
        cin >> a;
        num.push_back(a);
        if (a >= 0)
            flag = false;
    }
    if (flag) {
        printf("%d %d %d
", 0, num[0], num[num.size() - 1]);
        return 0;
    }
    dp[0] = num[0];
    for (int i = 1; i < n; i++) {
        if (dp[i - 1] + num[i] <= num[i]) {
            //如果加上num[i]反而变小了；
            dp[i] = num[i];
            root[i] = i;//从新开始开路径
        }
        else {
            //如果加上变大了
            dp[i] = num[i] + dp[i - 1];
            root[i] = root[i - 1];
        }
    }
    int k = 0;
    for (int i = 1; i < n; i++) {
        if (dp[i] > dp[k])
            k = i;
    }
    printf("%d %d %d
", dp[k], num[root[k]], num[k]);
    return 0;
}