编辑代码

#include <stdio.h>

int findPattern(char text[], char pattern[], int textLen, int patternLen) {
    int index = -1;

    if (textLen <= 0 || patternLen <= 0 || textLen < patternLen) {
        return index;
    }

	int i, j;
    for (i=0; i<textLen-patternLen+1; ++i) {
        for (j = 0; j < patternLen; ++j) {
            if (text[i + j] != pattern[j]){
                break;
            }
        }

        if (j == patternLen) {
            index = i;
            break;
        }
    }

    return index;
}

int main() {
	printf("%d\n", findPattern("", "", 0, 0));
	printf("%d\n", findPattern("HELLO_WORLD", "", 11, 0));
	printf("%d\n", findPattern("HELLO_WORLD", "WOR", 11, 3));
	printf("%d\n", findPattern("HELLO_WORLD", "XYZ", 11, 3));
	printf("%d\n", findPattern("HELLO_WORLD", "HELLO_WORLD_", 11, 12));
	return 0;
}findPatternfindPattern