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#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "math.h"

int GetMaxSubLen(char *d, int dSize, int maxCost)
{
    int left = 0;
	int right = 0;
	int len = 0;
	int sum = 0;
	while(right < dSize) {
	    sum += d[right];
		right++;
		if (sum <= maxCost) {
			len = len > (right - left) ? len : (right - left);
		}
		while (sum > maxCost) {
			sum -= d[left];
			left++;
		}

	}
    len = len > (right - left) ? len : (right - left);
	return len;
}

int equalSubstring(char * s, char * t, int maxCost){
	int maxLen = 0;
	if ((s == NULL) || (t == NULL)) {
	    return maxLen;
	}    
    int lenS = strlen(s);
	int lenT = strlen(t);
	if (lenS != lenT) {
	    return maxLen;
	}
	char *d = (char *) malloc(lenS + 1);
	(void)memset(d, 0, lenS + 1);
	for (int i = 0; i < lenS; i++) {
		d[i] = s[i] > t[i] ? (s[i] - t[i]) : (t[i] - s[i]);
		// printf("d[%d] [%d]\n", i, d[i]);
	}
    maxLen = GetMaxSubLen(d, lenS, maxCost);
	return maxLen;
}

void TestCase01()
{
    char s[] = "abcd";
	char t[] = "bcdf";
	int maxCost = 3;
	int maxLen = equalSubstring(s, t, maxCost);
    printf("maxLen %d\n", maxLen);
}

void TestCase02()
{
    char s[] = "abcd";
	char t[] = "cdef";
	int maxCost = 3;
	int maxLen = equalSubstring(s, t, maxCost);
    printf("maxLen %d\n", maxLen);
}

void TestCase03()
{
    char s[] = "abcd";
	char t[] = "acde";
	int maxCost = 0;
	int maxLen = equalSubstring(s, t, maxCost);
    printf("maxLen %d\n", maxLen);
}

int main ()
{
	TestCase01(); // 3
	TestCase02(); // 1
	TestCase03(); // 1
    // printf("-----Life is short, do somthing meaningful!\n");
	system("pause");
	system("cls");

	return 0;
}