<挑战程序设计竞赛> poj 3320 Jessica's Reading Problem 双指针

地址 http://poj.org/problem?id=3320

解答

使用双指针 在指针范围内是否达到要求

若不足要求则从右进行拓展  若满足要求则从左缩减区域

代码如下  正确性调整了几次 然后被输入卡TLE卡了很久都没意识到......... 

#include <iostream>
#include <map>
#include <set>
#include <algorithm>
#include <assert.h>
#include <stdio.h>


using namespace std;

int n, m;

const int MAX_N = 1000010;

int v[MAX_N];

set<int> setint;

int minLen = 999999;


int main()
{
    cin >> n;

    for (int i = 0; i < n; i++) {
        //cin >> v[i];
        scanf("%d",&v[i]);
        setint.insert(v[i]);
    }

    int total = setint.size();

    int l = 0; int r = 0;
    map<int, int> mapcover;
    mapcover[v[l]]++;
    int count = 1;

    while(1) {
        while (count < total) {
            r++;
            if (r >= n) {
                printf("%d
", minLen);
                return 0;
            }
            mapcover[v[r]]++;
            if (mapcover[v[r]] == 1) {
                //说明添加了一个新类型
                count++;
            }
        }

        if (count < total) {
            break;
        }

        minLen = min(minLen, r - l + 1);
        
        //尝试缩小整个范围 从左端减少
        mapcover[v[l]]--;
        if (mapcover[v[l]] == 0) {
            //说明减少了一个种类
            count--;
        }
        l++;
    }


    printf("%d
", minLen);
    return 0;
}

#include <iostream>
#include <map>
#include <set>
#include <algorithm>
#include <assert.h>
#include <stdio.h>


using namespace std;

int n, m;

const int MAX_N = 1000010;

int v[MAX_N];

set<int> setint;

int minLen = 999999;

int main()
{
    cin >> n;

    for (int i = 0; i < n; i++) {
        scanf("%d",&v[i]);
        setint.insert(v[i]);
    }

    int total = setint.size();

    int l = 0; int r = 0;
    map<int, int> mapcover;
    mapcover[v[l]]++;
    int count = 1;
    while (1) {
        if (count < total) {
            r++;
            if (r >= n) break;
            mapcover[v[r]]++;
            //添加了一个新元素 那么元素种类计数+1
            if (mapcover[v[r]] == 1) count++;
            
        }
        else if(count == total) {
            minLen = min(minLen, r - l + 1);
            mapcover[v[l]]--;
            if (mapcover[v[l]] == 0) {
                count--;
            }
            l++;
            if (l >= n) break;
            if (l > r) {
                r = l;
            }
        }
        else {
            assert(0);
        }

    }

    printf("%d
",minLen);


    return 0;
}