Codeforces Round #424 (Div. 2, rated, based on VK Cup Finals) Problem A - B
Array of integers is unimodal, if:
- it is strictly increasing in the beginning;
- after that it is constant;
- after that it is strictly decreasing.
The first block (increasing) and the last block (decreasing) may be absent. It is allowed that both of this blocks are absent.
For example, the following three arrays are unimodal: [5, 7, 11, 11, 2, 1], [4, 4, 2], [7], but the following three are not unimodal:[5, 5, 6, 6, 1], [1, 2, 1, 2], [4, 5, 5, 6].
Write a program that checks if an array is unimodal.
The first line contains integer n (1 ≤ n ≤ 100) — the number of elements in the array.
The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 1 000) — the elements of the array.
Print "YES" if the given array is unimodal. Otherwise, print "NO".
You can output each letter in any case (upper or lower).
6
1 5 5 5 4 2
YES
5
10 20 30 20 10
YES
4
1 2 1 2
NO
7
3 3 3 3 3 3 3
YES
In the first example the array is unimodal, because it is strictly increasing in the beginning (from position 1 to position 2, inclusively), that it is constant (from position 2 to position 4, inclusively) and then it is strictly decreasing (from position 4 to position 6, inclusively).
题目大意 给定一个数组,判断它是否是单峰的。一个数组是单峰的是指它的最大值出现的位置是连续的,其左侧严格递增,右侧严格递减。
先找出数组中的最大值,然后while到遇到最大值停止(边判断),然后while把最大值的连续一段水掉,然后再while到数组结尾。
Code
1 /** 2 * Codeforces 3 * Problem#831A 4 * Accepted 5 * Time:15ms 6 * Memory:2052k 7 */ 8 #include <iostream> 9 #include <cstdio> 10 #include <ctime> 11 #include <cmath> 12 #include <cctype> 13 #include <cstring> 14 #include <cstdlib> 15 #include <fstream> 16 #include <sstream> 17 #include <algorithm> 18 #include <map> 19 #include <set> 20 #include <stack> 21 #include <queue> 22 #include <vector> 23 #include <stack> 24 #include <cassert> 25 #ifndef WIN32 26 #define Auto "%lld" 27 #else 28 #define Auto "%I64d" 29 #endif 30 using namespace std; 31 typedef bool boolean; 32 const signed int inf = (signed)((1u << 31) - 1); 33 const signed long long llf = (signed long long)((1ull << 61) - 1); 34 const double eps = 1e-6; 35 const int binary_limit = 128; 36 #define smin(a, b) a = min(a, b) 37 #define smax(a, b) a = max(a, b) 38 #define max3(a, b, c) max(a, max(b, c)) 39 #define min3(a, b, c) min(a, min(b, c)) 40 template<typename T> 41 inline boolean readInteger(T& u){ 42 char x; 43 int aFlag = 1; 44 while(!isdigit((x = getchar())) && x != '-' && x != -1); 45 if(x == -1) { 46 ungetc(x, stdin); 47 return false; 48 } 49 if(x == '-'){ 50 x = getchar(); 51 aFlag = -1; 52 } 53 for(u = x - '0'; isdigit((x = getchar())); u = (u << 1) + (u << 3) + x - '0'); 54 ungetc(x, stdin); 55 u *= aFlag; 56 return true; 57 } 58 59 int n; 60 int *a; 61 int maxv = 0; 62 63 inline void init() { 64 readInteger(n); 65 a = new int[(n + 1)]; 66 for(int i = 1; i <= n; i++) { 67 readInteger(a[i]); 68 smax(maxv, a[i]); 69 } 70 } 71 72 inline void solve() { 73 int last; 74 int i = 1; 75 while(a[i] < maxv) { 76 if(i != 1) { 77 if(a[i - 1] >= a[i]) { 78 puts("NO"); 79 return; 80 } 81 } 82 i++; 83 } 84 while(a[i] == maxv && i <= n) i++; 85 while(i <= n) { 86 if(a[i] >= a[i - 1]) { 87 puts("NO"); 88 return; 89 } 90 i++; 91 } 92 puts("YES"); 93 } 94 95 int main() { 96 init(); 97 solve(); 98 return 0; 99 }
题目大意 给定字母的映射,然后映射一个字符串,非字母字符保留。
依题意乱搞即可。
Code
1 /** 2 * Codeforces 3 * Problem#831B 4 * Accepted 5 * Time:15ms 6 * Memory:2052k 7 */ 8 #include <iostream> 9 #include <cstdio> 10 #include <ctime> 11 #include <cmath> 12 #include <cctype> 13 #include <cstring> 14 #include <cstdlib> 15 #include <fstream> 16 #include <sstream> 17 #include <algorithm> 18 #include <map> 19 #include <set> 20 #include <stack> 21 #include <queue> 22 #include <vector> 23 #include <stack> 24 #include <cassert> 25 #ifndef WIN32 26 #define Auto "%lld" 27 #else 28 #define Auto "%I64d" 29 #endif 30 using namespace std; 31 typedef bool boolean; 32 const signed int inf = (signed)((1u << 31) - 1); 33 const signed long long llf = (signed long long)((1ull << 61) - 1); 34 const double eps = 1e-6; 35 const int binary_limit = 128; 36 #define smin(a, b) a = min(a, b) 37 #define smax(a, b) a = max(a, b) 38 #define max3(a, b, c) max(a, max(b, c)) 39 #define min3(a, b, c) min(a, min(b, c)) 40 template<typename T> 41 inline boolean readInteger(T& u){ 42 char x; 43 int aFlag = 1; 44 while(!isdigit((x = getchar())) && x != '-' && x != -1); 45 if(x == -1) { 46 ungetc(x, stdin); 47 return false; 48 } 49 if(x == '-'){ 50 x = getchar(); 51 aFlag = -1; 52 } 53 for(u = x - '0'; isdigit((x = getchar())); u = (u << 1) + (u << 3) + x - '0'); 54 ungetc(x, stdin); 55 u *= aFlag; 56 return true; 57 } 58 59 int n; 60 char a[1005]; 61 char b[1005]; 62 map<char, char> ctc; 63 64 const char utl = 'a' - 'A'; 65 66 inline void init() { 67 gets(a); 68 gets(b); 69 for(int i = 0; a[i]; i++) { 70 ctc[a[i]] = b[i]; 71 ctc[a[i] - utl] = b[i] - utl; 72 } 73 } 74 75 inline void solve() { 76 gets(a); 77 for(int i = 0; a[i]; i++) { 78 if((a[i] >= 'a' && a[i] <= 'z') || (a[i] >= 'A' && a[i] <= 'Z')) { 79 putchar(ctc[a[i]]); 80 } else { 81 putchar(a[i]); 82 } 83 } 84 } 85 86 int main() { 87 init(); 88 solve(); 89 return 0; 90 }