• 常见面试题学习(4)


    1. 给出一个有N个数字(-1000..1000,N<=10^5)的环状序列,求一个和最大的连续子序列。

    http://www.cppblog.com/baby-fly/archive/2010/08/04/122213.aspx?Pending=true 

    来源于单调队列的应用

    #include<iostream>
    #include
    <queue>
    using namespace std;
    #define INF 0x3fffffff
    #define maxn 100010
    int num[maxn],sum[maxn];
    int main()
    {
    int T;
    int N,K,n;
    cin
    >>T;
    while(T--)
    {
    cin
    >>N>>K;
    sum[
    0]=0;
    for(int i=1;i<=N;i++)
    {
    cin
    >>num[i];
    sum[i]
    =sum[i-1]+num[i];
    }
    for(int i=N+1;i<N+K;i++)
    {
    sum[i]
    =sum[i-1]+num[i-N];
    }
    n
    =N+K-1;

    deque
    <int> q;
    q.clear();

    int ans=-INF;
    int start,end;
    //[j-kj] 枚举以j结尾的区间,找[j-k,j]中sum最小的i
    for(int j=1;j<=n;j++)
    {
    while(!q.empty() && sum[j-1]<sum[q.back()])
    q.pop_back();
    while(!q.empty() && q.front()<(j-K))
    q.pop_front();
    q.push_back(j
    -1);
    if(sum[j]-sum[q.front()]>ans)
    {
    ans
    =sum[j]-sum[q.front()];
    start
    =q.front()+1;
    end
    =j;
    }
    }
    cout
    <<ans<<" "<<start<<" "<<(end>N?end%N:end)<<endl;
    }
    }

      2. 一道微软的面试题

    http://www.cnblogs.com/qsort/archive/2011/05/30/2063605.html 本着测试先行的原则 。。。 是啊,这得闲考虑多个情况后才编码

    #include <stdio.h>
    #include
    <assert.h>
    #include
    <string.h>

    // Test cases for leading & trailing spaces.
    char arr00[] = "hello_world";
    char arr01[] = "hello world";
    char arr02[] = " hello world";
    char arr03[] = "hello world ";
    char arr04[] = " hello world ";
    // Test cases for consecutive spaces.
    char arr05[] = "hello world";
    char arr06[] = " hello world ";
    // Test cases for spaces around new-lines.
    char arr07[] = "hello \n world ";
    char arr08[] = " hello world \n ";
    char arr09[] = "\n hello world \n ";
    // Corner cases
    char arr10[] = " ";
    char arr11[] = "\n";
    char arr12[] = " \n ";

    void filter_spaces(char *str, size_t len)
    {
    char *dst = str + len - 1;
    char *curr = str + len - 1;

    while (*curr == ' ' && curr >= str)
    --curr; // remove trailing spaces;
    if (curr < str) { // all spaces.
    *str = '\0';
    return;
    }
    int after_space = 0;
    int around_newline = 0;
    while (curr >= str) {
    switch (*curr) {
    case ' ':
    if (after_space) { // a space followed by another space, omit it.
    --curr;
    }
    else if (around_newline) { // a space around a newline, omit it.
    --curr;
    }
    else {
    after_space
    = 1;
    *dst-- = *curr--;
    }
    break;
    case '\n':
    around_newline
    = 1;
    if (after_space) { // remove last recorded space.
    assert(*(dst + 1) == ' ');
    ++dst;
    after_space
    = 0;
    }
    *dst-- = *curr--;
    break;
    default: // other chars
    *dst-- = *curr--;
    after_space
    = 0;
    around_newline
    = 0;
    break;
    }
    }
    ++dst;
    if (*dst == ' ') // remove leading spaces.
    ++dst;
    // now the filtered string size is ( (str + size) - dst + 1 ),
    // including the trailing '\0'
    memmove(str, dst, (str + len) - dst + 1);

    }

    #define TEST_STR(str) do {\
    filter_spaces(str, strlen(str));\
    printf(#str
    ": \"%s\"\n", str);\
    }
    while(0);

    int main(int argc, char *argv[])
    {
    TEST_STR(arr00);
    TEST_STR(arr01);
    TEST_STR(arr02);
    TEST_STR(arr03);
    TEST_STR(arr04);
    TEST_STR(arr05);
    TEST_STR(arr06);
    TEST_STR(arr07);
    TEST_STR(arr08);
    TEST_STR(arr09);
    TEST_STR(arr10);
    TEST_STR(arr11);
    TEST_STR(arr12);

    return 0;
    }

      

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  • 原文地址:https://www.cnblogs.com/hitwtx/p/2152945.html
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