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q0456.c
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q0456.c
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//
// q0456.c
// LeetCode
//
// Created by NowOrNever on 15/02/2020.
// Copyright © 2020 DoubleL. All rights reserved.
//
#include "q0456.h"
#include "../common.h"
//456. 132 Pattern
//Medium
//
//1029
//
//70
//
//Add to List
//
//Share
//Given a sequence of n integers a1, a2, ..., an, a 132 pattern is a subsequence ai, aj, ak such that i < j < k and ai < ak < aj. Design an algorithm that takes a list of n numbers as input and checks whether there is a 132 pattern in the list.
//
//Note: n will be less than 15,000.
//
//Example 1:
//Input: [1, 2, 3, 4]
//
//Output: False
//
//Explanation: There is no 132 pattern in the sequence.
//Example 2:
//Input: [3, 1, 4, 2]
//
//Output: True
//
//Explanation: There is a 132 pattern in the sequence: [1, 4, 2].
//Example 3:
//Input: [-1, 3, 2, 0]
//
//Output: True
//
//Explanation: There are three 132 patterns in the sequence: [-1, 3, 2], [-1, 3, 0] and [-1, 2, 0].
bool find132pattern(int* nums, int numsSize){
if (numsSize < 3) {
return false;
}
int stack[numsSize];
int stackLen = 0;
int mid = INT_MIN;
for ( int i = numsSize - 1; i >= 0; i-- ) {
//printf( "%d %d %d\n", nums[i], mid, stackLen ? stack[stackLen-1] : 0 );
if ( nums[i] < mid )
return true;
while( ( stackLen > 0 ) && ( nums[i] > stack[stackLen-1] ) ){
mid = stack[--stackLen];
}
stack[stackLen++] = nums[i];
}
return false;
}
int question456(){
int nums[] = {3,5,0,3,4};
bool result = find132pattern(nums, sizeof(nums) / sizeof(int));
printf("question456: %d\n", result);
return 0;
}